CO之NSString, NSArray, NSNumber

万物皆为对象


API(application  programming interface, 应用程序编程接口)
在程序调用的时候,一般说提供接口,即方法.


举例:
        //1.创建对象
        //2.两种方式:
        //(1)便利构造器(+ 号方法)
        NSString *str1 = [NSString stringWithFormat:@"iPhone%d", 5];
        NSLog(@"str1 = %@", str1);
        //(2)alloc + 初始化方法
        NSString *str2 = [[NSString alloc] initWithFormat:@"iPhone%d", 5];
        NSLog(@"str2 = %@", str2);
        //(3)根据字符串初始化OC字符串对象
        NSString *str3 = @"Lanou"; //指向的空间为常量区,存储常量字符串@"lanou"的地址
        NSLog(@"%p", str3);



        //2.求字符串长度
        NSUInteger len = [str1 length];
        NSLog(@"legth = %lu", len);
        //3.获取字符串中的某个字符
        unichar charac = [str1 characterAtIndex:2];
        NSLog(@"char = %c", charac);
        //4.判断是否以指定的字符串开头,或者一指定的字符串结尾
        //例如:判断一个字符串是否以http开头,是否以.com结束
        NSString *webUrl = [NSString stringWithFormat:@"http://www.baidu.com"];
        //判断是否以http开头
        BOOL isPrefix = [webUrl hasPrefix:@"http"];
        NSLog(@"isPrefix = %d", isPrefix);
        //判断是否以.com结尾
        BOOL isSuffix = [webUrl hasSuffix:@"com"];
        NSLog(@"isSuffix = %d", isSuffix);





        //5.查找指定字符串的范围
        NSString *webUrl = [NSString stringWithFormat:@"http://www.baidu.com"];
        NSRange range = [webUrl rangeOfString:@"baidu"];
        if (range.length == 0) {
            NSLog(@"没有找到对应的字符串");
        } else {
            //NSLog(@"location:%lu, length:%lu", range.location, range.length);
            //将NSRange类型的结构体变量转变成字符串对象
            NSLog(@"%@", NSStringFromRange(range));
        }



        //6.字符串截取(获取子字符串)
        //(1)获取给定下标之后的子串,包含指定下标对应的字符
        //对字符串进行操作,操作的是定义的字符串的副本.
        NSString *webUrl = [NSString stringWithFormat:@"http://www.baidu.com"];
        NSString *getSubStr = [webUrl substringFromIndex:11];
        NSLog(@"%@", getSubStr);
        //(2)获取给定下标之前的子串,从下标为0开始,但是不包括指定下标对应的字符
        NSString *getSubStr1 = [webUrl substringToIndex:11];
        NSLog(@"%@", getSubStr1);
        //(3)获取指定范围内的子串
        //例如:获取baidu
        NSString *getSubStr2 = [webUrl substringWithRange:NSMakeRange(11, 5)];
        NSLog(@"%@", getSubStr2);



        //7.字符串拼接
        NSString *str = [NSString stringWithFormat:@"lanou"];
        //lanou 后拼接 henan
        NSString *str1 = [str stringByAppendingString:@"henan"];
        NSLog(@"%@", str1);
        //lanou 后拼接 henan9ban
        NSString *str2 = [str stringByAppendingFormat:@"%@", str1]; //Format 可以在字符串里边加上格式串
        NSLog(@"%@", str2);





        //8.替换字符串
        NSString *str = [NSString stringWithFormat:@"lanou is a big big big company"];
        //将big 替换成 niubi
        NSString *str1 = [str stringByReplacingOccurrencesOfString:@"big" withString:@"niubi"];
        NSLog(@"%@", str1);
        //只将第一个big 替换成 niubi
        NSString *str2 = [str stringByReplacingCharactersInRange:NSMakeRange(11, 3) withString:@"niubi"];
        NSLog(@"%@", str2);





        //9.字符串比较
        NSComparisonResult result = [@"222" compare:@"333"];
        NSLog(@"result:%ld", result);



        //10.字符串和数值类型转换
        //1.@"123", 将字符串123转换成整数123
        //从第一个字符开始,如果在遇到除了空格之外的字符时,将前面的空格忽略掉,继续往下找,读到数字,知道遇到非数字时结束
        int a = [@" 1 d23" intValue];
        NSLog(@"%d", a);
        //2.@@"123", 将字符串123转换成浮点型123.00
        float b = [@"123" floatValue];
        NSLog(@"%.2f", b);
        //讲数字转为字符串对象
        NSString *str = [NSString stringWithFormat:@"%d", 9];
        NSLog(@"%@", str);



        //11.大小写转换操作
        //(1)将@"lan OU"全部转为大写
        NSString *str0 = [@"lan OU" uppercaseString];
        NSLog(@"%@", str0);
        //(2)将@"lan OU"全部转为小写
        NSString *str1 = [@"lan OU" lowercaseString];
        NSLog(@"%@", str1);
        //(3)将@"lan OU"每个单词的首字母大写
        NSString *str2 = [@"lan OU" capitalizedString];
        NSLog(@"%@", str2);



        NSMutableString *str = [NSMutableString stringWithFormat:@"lanouhenan"];
        //对于可变字符串的增删改方法,都是在远字符串基础上进行修改,所以修改之后原字符串的内容发生变化,所以无需返回值.
        //1.在字符串str基础上拼接Frank
        [str appendFormat:@"Frank"];
        NSLog(@"%@", str);
        //2.在字符串str基础上拼接Frank
        [str appendString:@"Frank"];
        NSLog(@"%@", str);
        //3.删除字符串,在原字符串基础上删除henan
        [str deleteCharactersInRange:NSMakeRange(5, 5)];
        NSLog(@"%@", str);
        //4.插入字符串,在原字符串基础上插入lanou
        [str insertString:@"wo ai " atIndex:0];
        NSLog(@"%@", str);
        //5.替换字符串,在原字符串基础上将第一个Frank替换成Duck
        [str replaceCharactersInRange:NSMakeRange(11, 5) withString:@"Duck"];
        NSLog(@"%@", str)