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I have types in distincts units with the same name and I have the unit name in a string. I need to access the specific type of this unit. How do I do that?

Example:

unit Unit1

type
   TFooType = (
      bar1,
      bar2
   );

then, I have another unit

unit Unit2

type
   TFooType = (
      foo1,
      foo2,
      foo3
   );

And, somewhere in my code I have the a string variable "UnitName" with the value 'Unit1' within it and I want to access the Unit1's "TFooType" type by the variable.

I'm using Delphi 2007

Sorry for my bad english.

Thanks in advance.

razlebe
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Haruki
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  • You should be using CLASSES not UNITS to do this. Learn some object oriented programming. Units are not to be manipulated this way. You can register classes, and an identifier (the class name or any string) and easily do a quick lookup from a string to a Class reference, which you can then instantiate an instance of the class. Or you can use delphi INTERFACES, and an IoC (inversion of control) container pattern. – Warren P May 21 '11 at 16:57

3 Answers3

11

You can't choose which units to include at run time. Units are a compile-time concept.

Furthermore, your two types, despite having the same base name, are completely distinct types. Elsewhere in your code, you cannot have a variable of type TFooType and arbitrarily decide whether to assign it values from both of those units. The variable can only hold values from one type.

You're going to have to think of some other way of accomplishing your real task. I invite you to post a new question describing what your real task is.

Rob Kennedy
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1

@Hrukai, Just like with lego, there's a lot you can do, but somethings just weren't designed to be used that way.

Sounds to me like your end goal is to access the type, and your starting point is a variable name. Had you implemented your variables as classes (OOP), you could simplly do Obj.ClassName to find its type... but also, had you chosen classes for your implementation, I predict this need (to access the type from the variable) would have never arisen in the first place.

Resist the urge to create a new pattern, and instead exploit the power of classes. http://www.delphibasics.co.uk/Article.asp?Name=OOExample

Sam
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The best you could do would be something like if name='Unit1' then T := Unit1.TFoo etc. But what can you do with T anyway? Since the enumerated types from the different units are different, it's hard to imagine being able to anything with T. In fact how would you even define T? The only thing I could imagine would be possible would be to return the type info but I'm letting my imagination run wild now!

David Heffernan
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  • RTTI has nothing to do with this. See Rob's answer - the two are totally different (and incompatible) types. You'd have to know in advance which one would be used, so you could declare the proper TFooType variable (eg., `var FT1: Unit1.TFooType; FT2: Unit2.TFooType;`). – Ken White May 20 '11 at 21:57
  • @Ken yeah I wrote that bit before I twigged the fact that it's only classes that can support what I was talking about. – David Heffernan May 20 '11 at 21:59
  • NP. Didn't downvote because of the first sentence in your original answer. :) – Ken White May 20 '11 at 22:08