24 Votes

Delphi: Check whether object or variable exists

Tip by Delphian | 2013-02-15 at 12:51

Sometimes you have to test whether an object or variable in Delphi exists at all or has already been initialized. How you do it, I show you in this tip.

We are using assigned() for this purpose. Assigned() returns true, if the object is existing and false if not. Let's look at an example:

var
  sl: TStringList;

...

if assigned(sl) then sl.free;

...

if assigned(sl)=false then sl:=TStringList.Create();

In this example, we only free the StringList in the case, the StringList exists and we are creating a new StringList only in the case, the StringList is not existing.

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