Need help in understanding "this" code

[shivang sarawagi]

public class CurrentConditionsDisplay implements Observer, DisplayElement {

private Subject weatherData;

public CurrentConditionsDisplay(Subject weatherData) {
this.weatherData = weatherData;
weatherData.registerObserver(this);
}

Can anyone help me in understanding the code inside the constructor

this.weatherData = weatherData;
weatherData.registerObserver(this);

registerObserver is a method in another class

Thanks

[Ralph Cook]

'this' is a keyword in java. It refers to the instance of the object in which the code is currently running.

To create a CurrentConditionsDisplay object in another class, you would use (evidently)

CurrentConditionsDisplay ccd = new CurrentConditionsDisplay(weatherData);

and after that, ccd would be a reference to the object instance you had created. The 'this' keyword refers to that object inside the CurrentConditionsDisplay code.

Evidently the registerObserver() method can take a reference to a CurrentConditionsDisplay object, probably it requires Observer. One has to be careful using 'this' within constructors, since, until the constructor has exited, the object is not fully formed. However, near the end of the constructor and just for purposes of putting it on an observer list, it's probably fine as illustrated here.

rc

[Campbell Ritchie]

There is a similar discussion here.

[Winston Gutkowski]

Campbell Ritchie wrote:There is a similar discussion here.

Ah, so we now have circular references. Since both Threads are by the same OP, might it not be better to remove one?

Winston

[fred rosenberger]

Winston Gutkowski wrote:Ah, so we now have circular references. Since both Threads are by the same OP, might it not be better to remove one?

Winston

yup.