I was reviewing this example for a little bit until the hint finally clicked. I opened the books code to help understand what was happening. The methods make sense, however something else caught my eye.

ComplexNumber class's methods, AddTo for example

public ComplexNumber AddTo(ComplexNumber c1)
{
ComplexNumber result = new ComplexNumber();
result.Real = this.Real + c1.Real;
result.Imaginary = this.Imaginary + c1.Imaginary;
return result;
}

I dont really understand the "this" keyword very well. and in this example I removed all the "this" keywords and it still worked perfectly. IE remove this.Real and turn it to just Real.

From what I do understand of (this), it represents the current object in the code that is executing. So this would usually just represent a class, and represent all of its fields or parameters. But I'm confused on why it would be used in this example?

You're exactly right. The value "this" is the object whose code is currently executing.

If you omit "this," then by default the program looks at the current object's properties to resolve unresolved references. In this case, if you say just "Real," the program looks around for a variable named Real but doesn't find one locally so it looks at the current object's properties and finds one named Real.

Sometimes I (and others) use "this" to emphasize the fact that the code is working with the current object as opposed to some other object or a local variable. In this case I did it to make it clear that there are two objects involved: this and c1.

But it's purely stylistic. You don't need to use "this" if you don't want to.

__________________
Rod

Rod Stephens, Microsoft MVP

Essential Algorithms: A Practical Approach to Computer Algorithms

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