oc笔记－－NSString用法

创建NSString对象

 /*使用实例方法创建NSString对象*/
        NSString *string1=[[NSString alloc]initWithFormat:@"学号12111"];//格式化创建字符串
        NSString *string2=[[NSString alloc]initWithFormat:@"机构名称：%@ 成立时间：%d",@"中嘉博众",2001];
        NSString *str1=[[NSString alloc]initWithString:string1];
        NSLog(@"%@",string1);
        NSLog(@"%@",string2);
        NSLog(@"%@",str1);
        /*使用类方法创建NSString对象*/
        NSString *string3=[NSString stringWithFormat:@"姓名：%@  年龄：%d",@"小明",20];
        NSLog(@"%@",string3);

其他用法

//计算字符串长度
        NSUInteger strlen=[str length];
        NSLog(@"%ld",strlen);

 //比较字符串对象是否相同（1）
        if([str isEqualToString:@"创建一个字符串常亮da"]){
            NSLog(@"两个字符串相等");
        }else{
            NSLog(@"两个字符串不相等");
        }
        //(2)
        if(str==str0){
            NSLog(@"两个字符串相等");
        }else{
            NSLog(@"两个字符串不相等");
        }

//两个字符串比较(逐个相比)比较大小
        NSComparisonResult result=[str compare:str3];
       // NSComparisonResult result1=[str caseInsensitiveCompare:str3];比较字符串
        NSLog(@"%ld",result);//返回-1则第二个数大  0为相等   1为第一个大
        if(result==NSOrderedAscending){
            NSLog(@"str<str3");
        }else if (result==NSOrderedDescending){
            NSLog(@"str>str3");
        }else{
            NSLog(@"str=str3");
        }

/*将对象类型转变为基础类型输出*/
        float num=24.32;
        NSString *str6=[NSString stringWithFormat:@"%f",num];
        int num1=[str6 intValue];    //强制转换
        NSLog(@"%d",num1);
        
        NSString *str7=@"http://localhost:8080/test/user=admin&pwd=123";
        const char *str8=[str7 UTF8String];   　//强制转换  用％s输出
        NSLog(@"%s",str8);
        NSLog(@"%@",str7);

/*判断字符串是否有指定的前缀*/
        BOOL result1=[string1 hasPrefix:@"学号"];
        NSLog(@"%d",result1);
        if([string1 hasPrefix:@"学号"]){
            NSLog(@"yes");
        }else{
            NSLog(@"no");
        }

/*判断字符串是否有指定的后缀*/
        BOOL result2=[string1 hasSuffix:@"1"];
        NSLog(@"%d",result2);
        if([string1 hasSuffix:@"1"]){
            NSLog(@"yes");
        }else{
            NSLog(@"no");
        }

/*分割字符串*/
        NSString *str9=@"哈哈  你呗拍类";
        NSString *str10=[str9 substringFromIndex:5];  //从第五个字符开始截取
        NSString *str11=[str9 substringToIndex:4];    //截取到第四个字符
        NSLog(@"%@",str10);
        NSLog(@"%@",str11);
        
        NSRange rang2=NSMakeRange(5,2);               //从第五位开始截取两位
        NSString *str12=[str9 substringWithRange:rang2];
        NSLog(@"%@",str12);

/*拼接字符串*/
        NSString *str13=@"hello";
        NSString *str14=[str13 stringByAppendingFormat:@" world"];
        NSLog(@"%@",str14);

/*大小写转换*/
        NSString *str15=@"hello world";
        NSLog(@"大写：%@",[str15 uppercaseString]);
        NSLog(@"小写：%@",[str15 lowercaseString]);
        NSLog(@"首字母大写：%@",[str15 capitalizedString]);

/*查找字符串的位置*/
        NSRange rang1=[str7 rangeOfString:@"http"];
        if(rang1.location==NSNotFound){
            NSLog(@"未找到");
        }else{
            NSLog(@"%@",NSStringFromRange(rang1));//快速输出范围
            NSLog(@"location:%ld  length:%ld",rang1.location,rang1.length);
        }

 //  替换

        NSString *string6 = [string2 stringByReplacingOccurrencesOfString:@"蓝鸥" withString:@"海鸥"];

        NSLog(@"%@", string6);

        NSRange range3 = NSMakeRange(3, 3);

        NSString *string7 = [string2 stringByReplacingCharactersInRange:range3 withString:@"HAHA 你中招了"];

        NSLog(@"%@", string7);

/*截取字符串 从网址中截取用户名和密码*/
        NSString *str=@"http://localhost:8090.cn?user=adminator&pwd=1234ABCD";
        NSRange range1=[str rangeOfString:@"user="];
        NSRange range2=[str rangeOfString:@"&pwd="];
        NSUInteger userlocation=range1.location+range1.length;
        NSUInteger userlength=range2.location-(range1.location+range1.length);
        NSRange userRange={userlocation,userlength};// 自定义一个结构体范围
        NSString *str1=[str substringWithRange:userRange];
        NSLog(@"user=%@",str1);
        NSUInteger strlen=[str length];
        NSUInteger pwdlocation=userlength+userlocation+range2.length;
        NSUInteger pwdlength=strlen-(userlength+userlocation+range2.length);
        NSRange pwdRange={pwdlocation,pwdlength};// 自定义一个结构体范围
        NSString *str2=[str substringWithRange:pwdRange];
        NSLog(@"pwd=%@",str2);

创建可变的字符串 

//nsstring父类 可变字符串时子类
        //创建可变字符串
        NSMutableString *mustr1=[[NSMutableString alloc]initWithFormat:@"Hello"];
        NSString *str=@"welcome to oc";
        //将不可变的字符串放在可变的字符串中
        mustr1=[NSMutableString stringWithString:str];
        NSLog(@"%@",mustr1);
        // 插入*(在指定位置进行插入)
        [mustr1 insertString:@" students" atIndex:7];
        NSLog(@"%@",mustr1);
        // 在末尾进行插入
        [mustr1 appendString:@" teacher"];
        [mustr1 appendFormat:@" %@",str];
        NSLog(@"%@",mustr1);
        //删除
        [mustr1 deleteCharactersInRange:NSMakeRange(8,9)];
        NSLog(@"%@",mustr1);
        //查找并删除
        NSRange rang=[mustr1 rangeOfString:@"teacher welcome to oc"];
        if(rang.location!=NSNotFound){
        [mustr1 deleteCharactersInRange:rang];
        }
        NSLog(@"%@",mustr1);
        //重新赋值
        [mustr1 setString:str];
        NSLog(@"%@",mustr1);
        //替换
        NSRange rang1=[mustr1 rangeOfString:@"oc"];
        [mustr1 replaceCharactersInRange:rang1 withString:@"IOS"];
        NSLog(@"%@",mustr1);