potential leak of an object allocated and stored into ...

出现了标题的错误

查了一通，内存管理的问题

http://stackoverflow/questions/9286782/potential-leak-of-an-object-allocated-and-stored-into-annot

https://developer.apple/library/mac/#documentation/Cocoa/Conceptual/MemoryMgmt/Articles/mmRules.html

这个例子很好：

You could also implement the fullName method like this:

- (NSString *)fullName {

    NSString *string = [NSString stringWithFormat:@"%@ %@",

                                 self.firstName, self.lastName];

    return string;

}

Following the basic rules, you don’t own the string returned by stringWithFormat:, so you can safely return the string from the method.

By way of contrast, the following implementation is wrong:

- (NSString *)fullName {

    NSString *string = [[NSString alloc] initWithFormat:@"%@ %@",

                                         self.firstName, self.lastName];

    return string;

}