初始化时需要setLength一个动态数组吗？ [英] Do I need to setLength a dynamic array on initialization?

问题描述

type Tmyclass = class(TObject)
  somearray: array of TSometype
  FBool: Boolean;
  Fint: Integer;
  Fstr: string;
  constructor Create;
  destructor Destroy; override;
end;

implementation

constructor Tmyclass.Create;
begin
  inherited;
  SetLength(somearray,0); //is this needed?
end;

destructor TmyClass.Destroy;
begin
  SetLength(somearray,0); //this IS needed!
  inherited;
end;

还有什么类型在创建时初始化？例如我在课堂上宣布的。
是FBool guranteed是假的？
是FInt guranteed为0？
是Fstr guranteed要'？

Also what types are initialized on creation? For example what I declared in the class. is FBool guranteed to be false? is FInt guranteed to be 0? is Fstr guranteed to be ''?

当地的？只有字符串？

我使用Delphi XE。

I use Delphi XE.

推荐答案

属性对象的内存在对象构造（堆分配）上初始化为0，因此通常您不需要初始化属于类的任何属性，默认值（零内存）为：

All the memory belonging to objects are initialized to 0 on object construction (heap allocation), so usually you don't need to initialize anything belonging to a class, default values (zero memory) are:

• 字符串将为''


• 整数将为0


• 浮点变量将为0
• 
  
• boolean将为false


• 指针和对象引用将为零


• 动态数组将包含零个元素。 / li>
  

• strings will be ''
• integers will be 0
• floating point variables will be 0
• boolean will be false
• pointers and object references will be nil
• dynamic arrays will contain zero elements.

等等。

对于本地变量和与堆栈相关的任何内容，它将包含垃圾，因此在使用变量之前，您有责任提供有意义的值。

For local variables and anything related to stack, it will contain garbage, so you're responsible to provide a meaningful value before using the variables.

如下所示：

procedure Something;
var
  x: Integer;
begin
  ShowMessage(IntToStr(X));
end;

将显示一个随机值。

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