NSString 的内存地址

#import <Foundation/Foundation.h>

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        // insert code here...
        NSString *str1 = @"xiaoming";
        
        NSString *str2 = [NSString stringWithFormat:@"xiaoming"];
        
        NSString *str3 = [NSString stringWithFormat:@"xiaoming"];
        
        NSString *str4 = @"xiaoming";
        
        NSLog(@"\nstr1: %p\nstr2: %p \nstr3: %p \nstr4: %p", str1, str2, str3, str4);
    }
    return 0;
}

2019-06-26 09:40:52.294925+0800 test[804:77187] 
str1: 0x100001048
str2: 0xeae43525019535b5 
str3: 0xeae43525019535b5 
str4: 0x100001048
Program ended with exit code: 0

这段结果 :通过类方法stringWithFormat自定义创建的字符串会放在堆里面，即使字符串内容相同，也会再次开辟新空间，然后指针就是在栈里面，保存对象的地址 有所违背, 查找原因中