E2511类型参数'T'必须是类类型编译器错误意味着什么? [英] What does the E2511 Type parameter 'T' must be a class type compiler error mean?
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问题描述
遵循我的上一个问题,我试图从一个答案中编译代码
类型
TSearchableObjectList< T> = class(TObjectList< T>)
end;
编译器不会编译它并报告这个错误信息:
[dcc32错误]:E2511类型参数'T'必须是类类型
这个错误信息是什么意思,我该如何修复代码? ; 包含一个通用约束, T
是一个类。类型声明如下:
类型
TObjectList< T:class> = class(TList< T>)
...
end;
您可能认为约束是继承的,但事实并非如此。所以你需要在你的课堂中包含约束。指定约束如下:
类型
TSearchableObjectList< T:class> = class(TObjectList< T>)
...
end;
Following my previous question, I am attempting to compile the code from one of the answers there.
type
TSearchableObjectList<T> = class(TObjectList<T>)
end;
The compiler will not compile this and reports this error message:
[dcc32 Error]: E2511 Type parameter 'T' must be a class type
What does this error message mean, and how should I fix the code?
解决方案
TObjectList<T>
includes a generic constraint that T
is a class. The type declaration is as follows:
type
TObjectList<T: class> = class(TList<T>)
...
end;
You might think that constraints are inherited, but that is not the case. And so you need to include the constraint in your class. Specify the constraint like so:
type
TSearchableObjectList<T: class> = class(TObjectList<T>)
...
end;
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