Is there automatic initialization for attributes?

问题

I was wondering if attributes were automatically set to nil during an object's initialization or they have random values?

回答1:

If this question is indicative of Objective-C, I'd say that you should initialize all values of a variable when you declare them.

Explicitly initializing variables when they're declared gives you two benefits:

1. There is no ambiguity in what the value of the variable is.
2. Readability for others who read your code.

回答2:

All instance variables are guaranteed to be initialized to nil or zero. This goes for non-object iVars as well, (int, BOOL, float).

回答3:

In Java, the data members of a class are set their default values. I.e string = null ,int =0.

来源：https://stackoverflow.com/questions/4528098/is-there-automatic-initialization-for-attributes