Delphi Language Guide - Learn Delphi

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Delphi Language Guide

Version 10.3 Rio

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November, 2019

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CONTENTS

Language Overview....................................................................................................... 15 Program Organization ................................................................................................ 15 Delphi Source Files ................................................................................................... 16 Other Files Used to Build Applications .................................................................. 16 Compiler-Generated Files ...................................................................................... 17 Example Programs ...................................................................................................... 17 A Simple Console Application............................................................................... 18 A More Complicated Example ............................................................................. 19 A VCL Application ................................................................................................... 20

Programs and Units Index .............................................................................................. 23 Topics ............................................................................................................................ 23

Programs and Units (Delphi).......................................................................................... 24 Program Structure and Syntax .................................................................................. 24 The Program Heading............................................................................................. 24 The Program Uses Clause ....................................................................................... 25 The Block ................................................................................................................... 25 Unit Structure and Syntax ........................................................................................... 26 The Unit Heading ..................................................................................................... 27 The Interface Section .............................................................................................. 27 The Implementation Section.................................................................................. 27 The Initialization Section.......................................................................................... 28 The Finalization Section........................................................................................... 28 Unit References and the Uses Clause ...................................................................... 29 The Syntax of a Uses Clause................................................................................... 29 Multiple and Indirect Unit References .................................................................. 30 Circular Unit References ......................................................................................... 31

Using Namespaces with Delphi .................................................................................... 32 Declaring Namespaces ............................................................................................. 33 Searching Namespaces............................................................................................. 34 Namespace search order...................................................................................... 34 A namespace search example ............................................................................ 34 Using Namespaces ..................................................................................................... 35 Fully qualified unit names ....................................................................................... 35 Multi-unit Namespaces ........................................................................................... 36

Fundamental Syntactic Elements Index...................................................................... 37 Topics ............................................................................................................................ 37

Fundamental Syntactic Elements (Delphi) ................................................................. 38 The Delphi Character Set........................................................................................... 38 Tokens............................................................................................................................ 39 Special Symbols ....................................................................................................... 39 Identifiers ................................................................................................................... 40

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Reserved Words ....................................................................................................... 41 Directives................................................................................................................... 42 Numerals ................................................................................................................... 44 Labels......................................................................................................................... 45 Character Strings ..................................................................................................... 45 Comments and Compiler Directives........................................................................ 46 in ........................................................................................................................................ 47 Expressions (Delphi)......................................................................................................... 48 Expressions .................................................................................................................... 48 Operators...................................................................................................................... 49 Arithmetic Operators .............................................................................................. 49 Boolean Operators .................................................................................................. 50 Complete Versus Short-Circuit Boolean Evaluation ........................................... 51 Logical (Bitwise) Operators .................................................................................... 52 String Operators ....................................................................................................... 54 Pointer Operators .................................................................................................... 54 Set Operators ........................................................................................................... 55 Relational Operators ............................................................................................... 56 Class and Interface Operators .............................................................................. 58 The @ Operator ........................................................................................................ 58 Operator Precedence............................................................................................ 58 Function Calls............................................................................................................... 60 Set Constructors........................................................................................................... 61 Indexes .......................................................................................................................... 61 Typecasts ...................................................................................................................... 62 Value Typecasts ....................................................................................................... 62 Variable Typecasts .................................................................................................. 62 Declarations and Statements (Delphi) ........................................................................ 64 Declarations ................................................................................................................. 64 Hinting Directives ..................................................................................................... 65 Statements ................................................................................................................... 66 Simple Statements....................................................................................................... 66 Assignment Statements .......................................................................................... 66 Procedure and Function Calls............................................................................... 67 Goto Statements ..................................................................................................... 67 Structured Statements ................................................................................................ 69 Compound Statements .......................................................................................... 70 With Statements ....................................................................................................... 70 If Statements............................................................................................................. 74 Case Statements ..................................................................................................... 76 Control Loops ........................................................................................................... 77 Blocks and Scope........................................................................................................ 86 Blocks ......................................................................................................................... 86 Scope ........................................................................................................................ 87

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Naming Conflicts ..................................................................................................... 87 Data Types, Variables, and Constants Index ............................................................. 88

Topics ............................................................................................................................ 88 About Data Types (Delphi)............................................................................................ 89 Simple Types (Delphi) ..................................................................................................... 91

Ordinal Types ............................................................................................................... 91 Integer Types ............................................................................................................ 92 Character Types ...................................................................................................... 95 Boolean Types .......................................................................................................... 96 Enumerated Types................................................................................................... 97 Subrange Types...................................................................................................... 102

Real Types...................................................................................................................104 String Types (Delphi) ..................................................................................................... 105

About String Types.....................................................................................................106 Short Strings................................................................................................................. 108 AnsiString ..................................................................................................................... 109 UnicodeString (the Default String Type).................................................................110 WideString................................................................................................................... 111 Working with null-Terminated Strings ...................................................................... 111

Using Pointers, Arrays, and String Constants......................................................112 Mixing Delphi Strings and Null-Terminated Strings ............................................113 Structured Types (Delphi).............................................................................................115 Alignment of Structured Types ................................................................................ 115 Sets............................................................................................................................... 115 Arrays ........................................................................................................................... 117 Static Arrays ............................................................................................................ 117 Dynamic Arrays ...................................................................................................... 118 Multidimensional Dynamic Arrays ....................................................................... 121 Array Types and Assignments .............................................................................. 122 String-Like Operations Supported on Dynamic Arrays.....................................122 Records (traditional) ................................................................................................. 123 Variant Parts in Records........................................................................................125 Records (advanced) ................................................................................................ 127 File Types (Win32)....................................................................................................... 128 Code Samples ........................................................................................................... 129 Pointers and Pointer Types (Delphi)............................................................................130 Overview of pointers.................................................................................................130 Using Extended Syntax with Pointers .................................................................. 132 Pointer Types .............................................................................................................. 132 Character Pointers ................................................................................................ 133 Byte Pointer.............................................................................................................133 Type-checked Pointers ......................................................................................... 133 Other Standard Pointer Types..............................................................................133 Procedural Types (Delphi) ........................................................................................... 134

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About Procedural Types...........................................................................................135 Method Pointers.....................................................................................................135

Procedural Types in Statements and Expressions ................................................. 137 Variant Types (Delphi) .................................................................................................. 138

Variants Overview ..................................................................................................... 138 Variant Type Conversions ........................................................................................ 140 Variants in Expressions............................................................................................... 142 Variant Arrays.............................................................................................................142 OleVariant .................................................................................................................. 143 Type Compatibility and Identity (Delphi) .................................................................. 143 Type Identity ............................................................................................................... 144 Type Compatibility .................................................................................................... 144 Assignment Compatibility ........................................................................................ 145 Data Types, Variables, and Constants Index (Delphi) ............................................ 146 Type Declaration Syntax .......................................................................................... 146 Variables (Delphi) ......................................................................................................... 148 Declaring Variables .................................................................................................. 148

Absolute Addresses ............................................................................................... 149 Dynamic Variables ................................................................................................ 150 Thread-local Variables..........................................................................................150 Declared Constants...................................................................................................... 151 True Constants ........................................................................................................... 151 Constant Expressions ............................................................................................. 154 Resource Strings ..................................................................................................... 155 Typed Constants........................................................................................................155 Array Constants...................................................................................................... 155 Record Constants .................................................................................................. 156 Procedural Constants ........................................................................................... 157 Pointer Constants...................................................................................................157 Writeable Typed Constants..................................................................................158 Procedures and Functions Index ................................................................................159 Topics .......................................................................................................................... 159 Procedures and Functions (Delphi)............................................................................160 About Procedures and Functions ........................................................................... 160 Declaring Procedures and Functions.....................................................................160 Procedure Declarations ....................................................................................... 161 Function Declarations ........................................................................................... 161 Calling Conventions.................................................................................................. 163 Forward and Interface Declarations......................................................................165 External Declarations ................................................................................................ 165 Linking to Object Files ........................................................................................... 166 Importing Functions from Libraries ...................................................................... 166 Overloading Procedures and Functions................................................................168 Local Declarations .................................................................................................... 171

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Nested Routines ..................................................................................................... 171 Parameters (Delphi)......................................................................................................172

About Parameters ..................................................................................................... 172 Parameter Semantics ............................................................................................... 173

Value and Variable Parameters ......................................................................... 173 Constant Parameters ............................................................................................ 174 Out Parameters......................................................................................................175 Untyped Parameters ............................................................................................. 176 String Parameters ...................................................................................................... 177 Array Parameters.......................................................................................................177 Open Array Parameters ....................................................................................... 178 Variant Open Array Parameters ......................................................................... 180 Default Parameters ................................................................................................... 181 Default Parameters and Overloaded Functions .............................................. 182 Default Parameters in Forward and Interface Declarations .......................... 183 Calling Procedures and Functions (Delphi) .............................................................. 183 Program Control and Parameters .......................................................................... 183 Open Array Constructors ......................................................................................... 184 Using the inline Directive .......................................................................................... 184 Anonymous Methods in Delphi...................................................................................186 Syntax .......................................................................................................................... 186 Using Anonymous Methods ..................................................................................... 188 Anonymous Methods Variable Binding ................................................................. 189 Variable Binding Illustration .................................................................................. 189 Anonymous Methods as Events .......................................................................... 190 Variable Binding Mechanism...............................................................................191 Utility of Anonymous Methods ................................................................................. 193 Variable Binding..................................................................................................... 193 Ease of Use..............................................................................................................194 Using Code for a Parameter ................................................................................ 195 Classes and Objects Index .......................................................................................... 197 Topics .......................................................................................................................... 197 Classes and Objects (Delphi)......................................................................................198 Class Types ................................................................................................................. 198 Inheritance and Scope ............................................................................................ 200 TObject and TClass................................................................................................201 Compatibility of Class Types ................................................................................ 201 Object Types .......................................................................................................... 201 Visibility of Class Members ....................................................................................... 202 Private, Protected, and Public Members .......................................................... 203 Strict Visibility Specifiers ......................................................................................... 203 Published Members ............................................................................................... 204 Automated Members (Win32 Only)....................................................................205 Forward Declarations and Mutually Dependent Classes ................................... 205

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Fields (Delphi) ................................................................................................................ 206 About Fields................................................................................................................206 Class Fields..................................................................................................................207

Methods (Delphi) .......................................................................................................... 208 About Methods..........................................................................................................209 Inherited .................................................................................................................. 210 Self............................................................................................................................ 210 Method Binding ......................................................................................................... 211 Static Methods ....................................................................................................... 211 Virtual and Dynamic Methods ............................................................................ 212 Class Methods............................................................................................................215 Ordinary Class Methods ....................................................................................... 215 Class Static Methods ............................................................................................. 216 Overloading Methods .............................................................................................. 216 Constructors ............................................................................................................... 217 Destructors .................................................................................................................. 219 Class Constructors ..................................................................................................... 220 Class Destructors........................................................................................................221 Message Methods.....................................................................................................222 Implementing Message Methods ....................................................................... 223 Message Dispatching ........................................................................................... 223

Properties (Delphi) ........................................................................................................ 224 About Properties........................................................................................................224 Property Access.........................................................................................................225 Array Properties ......................................................................................................... 227 Index Specifiers .......................................................................................................... 229 Storage Specifiers......................................................................................................229 Property Overrides and Redeclarations ................................................................ 230 Class Properties..........................................................................................................232

Events (Delphi)...............................................................................................................233 About Events .............................................................................................................. 233 Event Properties and Event Handlers ..................................................................... 233 Triggering Multiple Event Handlers ......................................................................... 235

Class References...........................................................................................................236 Class-Reference Types ............................................................................................. 236 Constructors and Class References....................................................................237 Class Operators ......................................................................................................... 238 The is Operator ....................................................................................................... 238 The as Operator ..................................................................................................... 238 Code Examples ......................................................................................................... 239

Exceptions (Delphi) ....................................................................................................... 240 About Exceptions ...................................................................................................... 240 When To Use Exceptions...........................................................................................240 Declaring Exception Types ...................................................................................... 241

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