通用TList在Delphi 2009中，IndexOf崩溃

问题描述

我已经看到很多Delphi 2009泛型中提到的错误，但从来没有预料到这样的基本的错误在Update 3中失败。如果列表包含1个或多个项目，则在通用TList或TObjectList上调用IndexOf将导致访问冲突：

 键入
 TTest = class（TObject）; 
 
程序DoTest; 
 var 
 list：TObjectList< TTest> ;; 
 t：TTest; 
 begin 
 list：= TObjectList< TTest>。创建; 
 try 
 t：= TTest.Create; 
 list.IndexOf（t）; //列表中没有项目，正确的结果-1 
 list.Add（t）; 
 list.IndexOf（t）; //访问冲突
 finally 
 list.Free; 
结束
结束
  

异常是EAccessViolation：访问冲突在地址0048974C在模块'testbed.exe'。地址00000000

使用调试DCU进行编译会导致generics.collections.pas中的问题 - FComparer成员未分配：

  function TList< T> .IndexOf（const Value：T）：Integer; 
 var 
 i：整数; 
 begin 
 for i：= 0 to Count  -  1 do 
 if FComparer.Compare（FItems [i]，Value）= 0 then 
 Exit（i）; 
结果：= -1; 
结束
  

这当然使得通用的TList几乎完全没用。由于更新3似乎没有修复这个错误，除了升级到XE之外，我有其他的追索权？

解决方案

有一个看这个问题。

特别是，尝试创建您的TList像这样

  TList< TTest> .Create（TComparer< TTest> .Default）; 
  

I've seen many mentions of bugs in Delphi 2009 generics, but never expected something so basic to fail in Update 3, no less. Calling IndexOf on a generic TList or TObjectList causes an access violation if the list contains 1 or more items:

type
  TTest = class( TObject );

procedure DoTest;
var
  list : TObjectList< TTest >;
  t : TTest;
begin
  list := TObjectList< TTest >.Create;
  try
    t := TTest.Create;
    list.IndexOf( t ); // No items in list, correct result -1
    list.Add( t );
    list.IndexOf( t ); // Access violation here
  finally
    list.Free;
  end;
end;

The exception is "EAccessViolation: Access violation at address 0048974C in module 'testbed.exe'. Read of address 00000000"

Compiling with debug DCUs leads to a problem in generics.collections.pas - the FComparer member is not assigned:

function TList<T>.IndexOf(const Value: T): Integer;
var
  i: Integer;
begin
  for i := 0 to Count - 1 do
    if FComparer.Compare(FItems[i], Value) = 0 then
      Exit(i);
  Result := -1;
end;

This of course makes the generic TList almost completely useless. Since Update 3 does not seem to have fixed this bug, do I have a recourse other than upgrading to XE?

解决方案

Have a look at this question. Generics problem

In particular, try creating your TList like this

TList<TTest>.Create(TComparer<TTest>.Default);

这篇关于通用TList在Delphi 2009中，IndexOf崩溃的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！