OC基础：Foundation框架之NSString和NSMutableString

 内容简介: Foundation框架之NSString和NSMutableString

 

第一部分》》》》NSString的使用

      基本用法

        //1.创建字符串

        //1.1常规创建，创建一个空的字符串
        //这样创建的字符串几乎没用，因为它们是空的而且还不可变
        //alloc创建
        NSString *str1 = [[NSString alloc] init];
        NSLog(@"str1 is:%@",str1);
        //用类方法创建
        NSString *str2 = [NSString string];
        NSLog(@"str2 is:%@",str2);
       
        //1.2格式化创建
        //alloc创建
        NSString *str3 = [[NSString alloc] initWithFormat:@"wlecome"];
        NSLog(@"str3 is:%@",str3);
        //类方法创建
        NSString *str4 = [NSString stringWithFormat:@"beijng"];
        NSLog(@"str4 is:%@",str4);
       
        //1.3快速创建
        NSString *strtemp = @"strtemp";
        NSLog(@"strtemp is %@",strtemp);
       
        //1.4下面两种方法已经不推荐使用
        //因为它们较为繁琐，且效果和快速创建是一样的，已经被弃用
        //NSString *str222 = [[NSString alloc] initWithString:@"222"];
        //NSString *str333 = [NSString stringWithString:@"333"];
       
        //1.5特别注意
        //这样并没有修改字符串，而是修改了指针的指向
        str1 =@"hello world";
        NSLog(@"str1 is %@",str1);

       
       
        //2.字符串的比较
        NSString *str6 = @"str6";
        NSString *str7 = @"str6";
        //2.1比较是不是同一个对象
        if([str6 isEqualTo:str7]){
            NSLog(@"str6和str7是同一个对象");
        }else{
            NSLog(@"不是同一个对象");

        }

        //2.2比较字符串的指针
        BOOL bool67 =(str6 == str7);
        if(bool67){
            NSLog(@"str6和 str7是同一个字符串");
        }else{
            NSLog(@"str6和str7不是同一个字符串");

        }

        //2.3比较字符串内容

        if ([str6 isEqualToString:str7]){
            NSLog(@"str7 和str6 字符串内容相同");
        }else{
            NSLog(@"str6和str7字符串内容不相同");

        }

        //2.4比较字符串的大小

        //使用NSComparisonResult接受结果
        //其原理是使用了枚举
        //typedef NS_ENUM(NSInteger, NSComparisonResult)
        //{NSOrderedAscending = -1L, NSOrderedSame, NSOrderedDescending};
        NSString *str8 = @"see you tommorrow";
        NSString *str9 = @"see you chen";
        NSComparisonResult result = [str8 caseInsensitiveCompare:str9];
        if(result ==NSOrderedAscending){
            NSLog(@"升序");
        }else if(result == NSOrderedSame){
            NSLog(@"相等");
        }else if(result == NSOrderedDescending){
            NSLog(@"降序");
        }
       
       
       
        //3.求字符串的长度,使用length
        NSInteger length = [str8 length];
        NSLog(@"str8 length is %ld",length);
       
       
       
        //4.字符串转换的问题
        //转为大写:uppercaseStrig
        NSString  *str8upper = [str8 uppercaseString];
        NSLog(@"str8upper is %@",str8upper);
        //转为小写:lowercaseString
        NSString *str8lower = [str8 lowercaseString];
        NSLog(@"str8lower is %@",str8lower);
        //首字母大写:capitalzedString
        NSString *str8capitalized =[str8 capitalizedString];
        NSLog(@"strcapitalized is %@",str8capitalized);
   
       
        //5.字符串和基本数据类型的转换
        //5.1转为整型
        NSString *str10 = @"123";
        NSInteger integervalue = [str10 integerValue];
        NSLog(@"integervalue is %ld",integervalue);
        //5.2转为浮点型
        NSString *str11 = @"1234.1";
        CGFloat  floatvalue = [str11 doubleValue];

        NSLog(@"floatvalue is %f",floatvalue);

        //5.3z换为布尔型

        BOOL boolvalue = [str10 boolValue];
        NSLog(@"boolalue is %d",boolvalue);
        //特别注意
        //如果赋值的字符串是false或者是0，结果是0
        //如果赋值的字符串是true或者其他不为0的字符串，结果是1
        NSString *truth = @"01";
        BOOL value = [truth boolValue];
        NSLog(@"value is %d",value);

       
        //6.从键盘输入赋值一个字符串
        //使用字符指针来引用一个字符串
        char *p = malloc(20);//开辟内存
        NSLog(@"请输入字符串：");
        scanf("%s",p);
        NSString *input = [NSString stringWithCString:pencoding:NSUTF8StringEncoding];

        NSLog(@"经过输入得到的字符串是：%@",input);

        用法补充

          //1.字符串截取
        //1.1从开始截取到最后
        NSString *str1 = @"hello world";
        NSString *str2 =[str1 substringFromIndex:1];
        NSLog(@"str2 is %@",str2);
        //1.2截取下前面的字符，不包括下标
        //包括最后一位的截取是11，如果是12就会数组越界
        NSString *str3 = [str1 substringToIndex:11];
        NSLog(@"str3 is %@",str3);
        //1.3使用结构体截取
        //从下标2位开始截取，截取6位
        NSRange range ={2, 6};
        NSString *str4 = [str1 substringWithRange:range];
        NSLog(@"str4 is %@",str4);
        //输出一个结构体
        NSLog(@"range is %@",NSStringFromRange(range));
       

       

        //2.获取字符
        //通过下标取字符
        NSString *str5 = @"I love you ,China";
        char c = [str5  characterAtIndex:3];
        NSLog(@"str5 中下标为3的字符是%c",c);
       
       
        //3.通过特殊字符分隔字符串
        NSString  *str6 = @"天平座，水瓶座，双子座，白羊座";
        NSArray *array = [str6 componentsSeparatedByString:@","];
        NSLog(@"输出这个数组是%@",array);
       
       
        //4.字符串的拼接
        NSString *str7 = @"take me";
        NSString *str8 = @"to your heart";
        //4.1 stringWithFormat
        NSString *str9 = [NSString stringWithFormat:@"%@ %@",str7,str8];
        NSLog(@"str9 is %@",str9 );
        //4.2 stringByAppendingString
        NSString *str10 = [str7 stringByAppendingString:str8];
        NSLog(@"str10 is %@",str10);
        //4.3 stringbyAppendingFormat
        NSString *str11 = [str7 stringByAppendingFormat:@" %@",str8];
        NSLog(@"str11 is %@",str11);
        //字符串拼接扩展一,自动增加了"/"
        NSString *str12 = [str7 stringByAppendingPathComponent:str8];
        NSLog(@"st12 is %@",str12);
        //字符串拼接扩展二，自动增加了“."
        NSString *str13 = [str7 stringByAppendingPathExtension:str8];
        NSLog(@"str13 is %@",str13);
       
       
        //5.字符串中的类型转换
        NSString *truth = @"false";
        BOOL value = [truth boolValue];
        NSLog(@"value is %d",value);
       
       
       
        //6.字符串查找
        //指定一个字符串，然后在原字符串中查找，返回的是一个结构体
        NSString *str14 = @"my hometown is zhumadian!";
        NSString *str15 = @"zhumadian";
        NSRange range2 = [str14 rangeOfString:str15];
        //输出结构体
        NSLog(@"range2 is %@",NSStringFromRange(range2));
        //通过获取结构体内容的方式输出
        NSLog(@"range2.location is%ld,range2 length is %ld",range2.location,range2.length);
        //通过判断的方式，查看是否找到了
        if(range2.location!= NSNotFound){
            NSLog(@"找到了字符串");
        }else{
            NSLog(@"没有找到字符串");
        }
        //在枚举中，NSnotFound被定义为NSIntegerMax,即最大值
        //输出的值是：9223372036854775807
        NSLog(@"输出NSNotFound：%ld",NSNotFound);
       
       
       
        //7.字符串替换
        //7.1使用已有字符串替换原字符串中的指定部分
        //StringByReplacingOccurrencesOfString
        NSString *str16 = @"the way to success";
        NSString *str17 = [str16 stringByReplacingOccurrencesOfString:@"success" withString:@"dream"];
        NSLog(@"替换后得到字符串str17：%@",str17);
        //7.2使用结构体替换
        //stringByReplacingCharactersInRange
        NSRange range3 = {3, 6};
        NSString *str18 = @"abcdefghijk";
        NSString *str19 = [str18 stringByReplacingCharactersInRange:range3 withString:@"ZS"];
        NSLog(@"str19 is %@",str19);

 

第二部分》》》》NSMutableString的使用

                 //NSMutableString是NSString的子类

        //NSMutbaleString是可变字符串，可以修改字符串的内容
       
        //1.创建可变字符串
        //注意：不可以使用快速创建的方式
        //1.1NSMutableString继承与NSString，同样通过alloc和类方法可以创建空的字符串
       
        //1.2普通方法创建
        NSMutableString *str1  =[[NSMutableString alloc]initWithString:@"welcome"];
        NSLog(@"str1 is %@",str1);
        NSMutableString *str2 = [NSMutableString stringWithString:@"it is ok!"];
        NSLog(@"str2 is %@",str2);
        //1.3通过格式化的方法来创建
        NSMutableString *str3 =[[NSMutableString alloc] initWithFormat:@"hello"];
        NSLog(@"str3 is %@",str3);
        NSMutableString *str4 = [NSMutableString stringWithFormat:@"world"];
        NSLog(@"str4 is %@",str4);
       
        //2.插入字符串
        //使用insertString
        [str4 insertString:@"hehe" atIndex:0];
        NSLog(@"str4从0位置插入字符串后：str4 = %@",str4);
  
        //3.删除字符串
        //首先构建好结构体
        //deleteCharactersInRange
        NSRange range = {1,2};
        [str4 deleteCharactersInRange:range];
        NSLog(@"str4删除字符串后得：str4 = %@",str4);

       

        //4.拼接字符串，是在本身上添加
        //4.1使用appendString
        [str4 appendString:@"ZS"];
        NSLog(@"使用appendString追加：str4=%@",str4);
        int index =90;
        //4.2使用appendFormat
        [str4 appendFormat:@"%d",index];
        NSLog(@"使用appendFormat添加：str4=%@",str4);

       

        //5.替换字符串
        NSRange range2 ={2,5};
        [str4 replaceCharactersInRange:range2 withString:@"替换"];

        NSLog(@"替换字符串后str4 = %@",str4);

第三部分》》》关于字符串的练习

   //题目：去掉字符串“123-456-789”中间的‘-’,得到新数组
    //第一种方法
    //分别截取获取数字，得到三个新数组，然后拼接
    NSString *str = @"123-456-789";
        NSString *str1 = [str substringWithRange:NSMakeRange(0, 3)];
        NSString *str2 = [str substringWithRange:NSMakeRange(4, 3)];
        NSString *str3 =[str substringWithRange:NSMakeRange(8, 3)];
        NSString *str4 = [str1 stringByAppendingFormat:@"%@%@",str2,str3];
        NSLog(@"方法一得到字符串：%@",str4);
       
    //第二种方法
    //替换的思想，直接把“-”替换掉
        NSString *str5 = [str  stringByReplacingOccurrencesOfString:@"-"withString:@""];
        NSLog(@"方法二得到字符串：%@",str5);
       
    //第三种方法
    //先分割得到数组，再组装拼接
        NSArray *array=[str componentsSeparatedByString:@"-"];
        NSString *str6 =[array componentsJoinedByString:@""];
        NSLog(@"str7 is %@",str6);