以往的Delphi版本，不支持接口的Weak，和UnSafe的引用，支持对象的Weak, UnSafe,而且仅在Android和Ios平台上支持。
现在Delphi XE10.1 Berlin终于增加了对接口的Weak, UnSafe的支持。
1.Weak
Weak引用，不影响引用计数器，但是如果对象被释放，Weak引用变量自动清0，来看例子：
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | type
TA=class(TInterfacedObject)
end;
procedureTForm1.Button1Click(Sender: TObject);
var
a:IInterface;
[weak]aweak:IInterface;
begin
a:=TA.Create;
aweak:=a;
Memo1.Lines.Add(Format('Ptr:%d', [NativeInt(Pointer(aweak))]));
a:=nil;
Memo1.Lines.Add(Format('Ptr:%d', [NativeInt(Pointer(aweak))]));
end;
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运行结果
weak引用非常适合用于两个对象需要互相引用的情况下，如果以往的引用，将无法让引用计数器清0.
如下面的例子，互相引用后，两个对象的计数器都不清0，导致内存泄漏
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 | type
ISimpleInterface =interface
procedureDoSomething;
procedureAddObjectRef (simple: ISimpleInterface);
end;
TObjectOne =class(TInterfacedObject, ISimpleInterface)
private
anotherObj: ISimpleInterface;
public
procedureDoSomething;
procedureAddObjectRef (simple: ISimpleInterface);
end;
.....................
procedureTObjectOne.AddObjectRef (simple: ISimpleInterface);
begin
anotherObj:=simple;
end;
.....................
var
one, two: ISimpleInterface;
begin
one := TObjectOne.Create;
two := TObjectOne.Create;
one.AddObjectRef (two);
two.AddObjectRef (one);
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这时候在Delphi XE10.1 Berlin下可以用weak引用，来快速方便的解决泄漏问题：
1 2 | private
[weak] anotherObj: ISimpleInterface;
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2.UnSafe
unsafe引用,不影响引用计数，但不会向Weak引用那样清零引用的变量。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | type
TA=class(TInterfacedObject)
end;
procedureTForm1.Button2Click(Sender: TObject);
var
a:IInterface;
[unsafe]aunsafe:IInterface;
begin
a:=TA.Create;
aunsafe:=a;
Memo1.Lines.Add(Format('Ptr:%d', [NativeInt(Pointer(aunsafe))]));
a:=nil;
Memo1.Lines.Add(Format('Ptr:%d', [NativeInt(Pointer(aunsafe))]));
end;
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运行结果
1 2 | Ptr:42640064
Ptr:42640064
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由于Unsafe引用，不影响应用计数器，下面的程序将导致内存泄漏：
1 2 3 4 5 6 7 | procedureTForm1.Button2Click(Sender: TObject);
var
[unsafe] one: ISomeInterface;
begin
one := TSomeObject.Create;
one.DoSomething;
end;
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https://www.cnblogs.com/hezihang/p/5536928.html#undefined