Object-c 之 字符串

#import <Foundation/Foundation.h>int main(int argc, const char * argv[]){    @autoreleasepool {        NSString *s1;        s1=[NSString stringWithFormat:@"%d + %d = %d",2,3,2+3];        NSLog(@"%@",s1);        NSLog(@"length:%ld",[s1 length]);                NSString *s2=@"2 + 3 = 5";        if([s1 isEqualToString:s2]){            NSLog(@"s1 isEqualToString:s2");        }else{            NSLog(@"s1 isNotEqualToString:s2");        }                if(s1 == s2){            NSLog(@"s1 == s2");        }else{            NSLog(@"s1 != s2");        }                if([s1 compare:s2]){            NSLog(@"s1 compare s2");        }else{            NSLog(@"s1 not compare s2");        }                        //拼接字符串        NSString *s3 =[NSString stringWithFormat:@"%@%@",s1,s2];        NSLog(@"%@",s3);                s3=@"";        s3=[s1 stringByAppendingString:s2];        NSLog(@"%@",s3);    }    return 0;}

运行结果