When do you use the “this” keyword? [closed]

Answer 1

1 - Common Java setter idiom:

 public void setFoo(int foo) {
     this.foo = foo;
 }

2 - When calling a function with this object as a parameter

notifier.addListener(this);

Answer 2

I got in the habit of using it liberally in Visual C++ since doing so would trigger IntelliSense ones I hit the '>' key, and I'm lazy. (and prone to typos)

But I've continued to use it, since I find it handy to see that I'm calling a member function rather than a global function.

Answer 3

'this.' helps find members on 'this' class with a lot of members (usually due to a deep inheritance chain).

Hitting CTRL+Space doesn't help with this, because it also includes types; where-as 'this.' includes members ONLY.

I usually delete it once I have what I was after: but this is just my style breaking through.

In terms of style, if you are a lone-ranger -- you decide; if you work for a company stick to the company policy (look at the stuff in source control and see what other people are doing). In terms of using it to qualify members, neither is right or wrong. The only wrong thing is inconsistency -- that is the golden rule of style. Leave the nit-picking others. Spend your time pondering real coding problems -- and obviously coding -- instead.

Answer 4

Another somewhat rare use for the this keyword is when you need to invoke an explicit interface implementation from within the implementing class. Here's a contrived example:

class Example : ICloneable
{
    private void CallClone()
    {
        object clone = ((ICloneable)this).Clone();
    }

    object ICloneable.Clone()
    {
        throw new NotImplementedException();
    }
}

Answer 5

I use it every time I can. I believe it makes the code more readable, and more readable code equals less bugs and more maintainability.

Answer 6

I can't believe all of the people that say using it always is a "best practice" and such.

Use "this" when there is ambiguity, as in Corey's example or when you need to pass the object as a parameter, as in Ryan's example. There is no reason to use it otherwise because being able to resolve a variable based on the scope chain should be clear enough that qualifying variables with it should be unnecessary.

EDIT: The C# documentation on "this" indicates one more use, besides the two I mentioned, for the "this" keyword - for declaring indexers

EDIT: @Juan: Huh, I don't see any inconsistency in my statements - there are 3 instances when I would use the "this" keyword (as documented in the C# documentation), and those are times when you actually need it. Sticking "this" in front of variables in a constructor when there is no shadowing going on is simply a waste of keystrokes and a waste of my time when reading it, it provides no benefit.