问题
I have this simple line of code:
int x;
x automatically has the value of 1. I don't set it to anything but when I debug, it shows that x is 1.
Does an int have a default value of 1?!
回答1:
No. int has an undefined default value. It just happens to be 1 in this case. It could just as easily be -18382 or 22 or 0xBAADF00D.
Always initialize your variables in C.
回答2:
The initial value is undefined, and in this case will be whatever happened to be in that memory location before x started using it.
(Depending on the surrounding code, you might find that in your specific case it's always 1, but you can't be sure of that.)
回答3:
No, on the contrary, x has no default value at all. What you're seeing is the garbage that the variable was placed upon when you created it.
回答4:
Instance variables are initialized to 0 before your initializer runs..
ref:
- Are instance variables set to nil by default in Objective-C?
来源：https://stackoverflow.com/questions/5980749/does-an-int-in-objective-c-have-a-default-value-of-1