using this in constructor

[shivang sarawagi]

public class PizzaStore {
SimplePizzaFactory factory;
public PizzaStore(SimplePizzaFactory factory) {
this.factory = factory;}
public Pizza orderPizza(String type) {
Pizza pizza;
pizza = factory.createPizza(type);
pizza.prepare();
pizza.bake();
pizza.cut();
pizza.box();
return pizza;
}
}

Can anyone tell the point of writing

this.factory=factory

within the constructor

[Winston Gutkowski]

shivang sarawagi wrote:Can anyone tell the point of writing

this.factory=factory

within the constructor

Yes, the compiler has two fields called 'factory' to deal with, so you need to indicate specifically which one you want it to use. By default it uses the one defined closest to the code (the parameter), so you need the this keyword to tell it that you mean the one defined for the instance.

Winston

[Randall Twede]

what it is doing is assigning the SimplePizzaFactory that was passed to it in the constructor to the member variable called factory. this is quite a common thing to do.

[dennis deems]

In other words, a parameter, whether for a method or a constructor, defines a variable with local scope. And if it so happens that this local variable is given the same name as an instance field, then the instance field is shadowed. Within the scope of the PizzaShop constructor, "factory" means the argument and not the instance field. So if we just wrote "factory=factory", we would merely be re-assigning to the local argument variable the value it already had, and the instance field would not be initialized.

[Mohamed Sanaulla]

There was a similar discussion here regarding the use of "this" keyword.
I think you should try to run the program without the "this" in the constructor and see the difference.

[Randall Twede]

Dennis, that is the best explanation i have ever heard.

[dennis deems]

Randall Twede wrote:Dennis, that is the best explanation i have ever heard.

Thank you!