Simple types with generics in Delphi

Question

Hi

How can I create a generic class only containing primitive types?

TField<T: xxx> = class  
private
    FValue: T;  
public  
    property Value: T read FValue write FValue;  
end;

I don't need interfaces, classes, etc, I only want booleans, ints, floats and so on...

Or there is another way to do that?

Thanks

Answer 1

If you want to limit the types that can be used for your generic can't you just check for valid types in the creation?

Answer 2

I'm not sure whether I'm getting your question right, but if you want a variable that can hold different primitive data types you might have a look at the Variant data type.

You would not need generics for that ;-)

Answer 3

According to Craig Stuntz' blog

The Delphi/Win32 type system isn’t rooted (built-in simple types, records, and classes don’t have a common ancestor), and primitive types can’t/don’t implement interfaces

so most likely you cannot restrict a generic class to primitive types (as opposed to C# which allows a "where T: struct")

Answer 4

You can use the "record" keyword, to constrain to value types (not reference types):

TField<T: record> = class   
private 
    FValue: T;   
public   
    property Value: T read FValue write FValue;   
end;