Objective C - Type Casting From NSString to Int

问题:

I have this bit of Objective C code, where I am casting a NSString to an int:

NSString *a=@"123abc";
NSInteger b=(int) a;
NSLog(@"b: %d",b);

And the NSLog produces this output:

b: 18396

Can anyone explain to me why this is happening?

I was under the impression type casting a string to an integer would get the numerical value from the string.

回答1:

You've got integer value of pointer to NSString object there. To parse string to integer you should do:

NSString *a = @"123abc";
NSInteger b = [a integerValue];

回答2:

To get the numerical value use :

int val = [stringObj intValue];

or for NSInteger :

NSInteger val = [stringObj integerValue];

回答3:

When you cast an object to an integer you will get the pointer to the memory address. You can call to [a integerValue] to get the integer value of the string.

Also when casting it is better to use NSInteger instate of int. Because when using a 64 bit operating system a NSInteger will be 64 bit.

回答4:

Or with Objective-C literals syntax:

@([a intValue]);