NSString* str = @" \n\n\n\n\n string\nstring \n \n \n ";
NSString* str2 = [str stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]]; //前后去空格
NSString* str3 = [str2 stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];//前后去行
NSLog(@"%@",str);
NSLog(@"%@",str2);
NSLog(@"%@",str3);