Object C 之字符串NSString

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Object C 之字符串NSString

OC中,字符串是由unichar(Unicode)字符组成.

NSString:不可变字符串(创建以后,内容和长度不能更改).

NSMutableString:可变字符串(创建以后, 内容还可以修改).

//创建字符串对象

    //(1)初始化方法

//    NSString *str = [[NSString alloc] initWithFormat:@"My "];

    

    //(2)便利构造器

//    NSString *string = [NSString stringWithFormat:@"haokun"];

    //(3)将C语言的字符串转化为OC的字符串对象;

//    char cStr[] = "iphone";

//    NSString *OCStr = [NSString stringWithUTF8String:cStr];

//1字符串长度

    NSString *str = [NSString stringWithFormat:@"lanou henan"];

    NSUInteger leng = str.length;

    NSLog(@"%lu", leng);

 //2判断字符串是否是  http 开头, 以png 结尾,如果是打印"这是一个有效连接",否则打印"连接出错";

    NSString *str = [NSString stringWithFormat:@".png"];

    //hasPrefix :判断字符串是否以某个字符串开头,返回值是bool类型

    //hasPrefix : 判断字符串是否以某个字符串结尾,返回值是bool类型

    BOOL isPrefix = [str hasPrefix:@"http"];

    BOOL isSuffix = [str hasSuffix:@"png"];

    if (isPrefix && isSuffix) {

        NSLog(@"");

    }

//3判断字符串是否相等

    NSString *str1 = [NSString stringWithFormat:@"Hello"];

    NSString *str2 = [NSString stringWithFormat:@"hello"];

    //判断地址

    if (str1 == str2) {

        NSLog(@"两个对象地址相等");

    } else {

        NSLog(@"两个对象地址不同");

    }

    //4判断内容

    if ([str2 isEqualToString:str1]) {

        NSLog(@"两个字符串内容相同");

    } else {

        NSLog(@"两个字符串内容不同");

    }

 //5获取子串

    NSString *string = [NSString stringWithFormat:@"keepcalm"];

    //获取keep

    NSString *keepString = [string substringToIndex:4];

    NSLog(@"%@", keepString);

    //获取calm

    NSString *calmString = [string substringFromIndex:4];

    NSLog(@"%@", calmString);

    //获取pca

//    NSMakeRange(NSUInteger loc, NSUInteger len)  快速创建 NSRange 类型的结构体变量

    NSString *pcaString = [string substringWithRange:NSMakeRange(3, 3)];

    NSLog(@"%@", pcaString);

 //6字符串拼接

    NSString *str = [NSString stringWithFormat:@"hehhe"];

    //拼接

    NSString *newStr = [str stringByAppendingFormat:@"aaaaa%dclass", 53453];

    NSLog(@"%@", newStr);

//7字符串替换

    NSString *str = [NSString stringWithFormat:@"hfdhfa"];

    //将a 换成aaa

    NSString *newStr = [str stringByReplacingOccurrencesOfString:@"a" withString:@"aaa"];

    NSLog(@"%@", newStr);

//8比较字符串

    NSString *str1 = [NSString stringWithFormat:@"lhdshf"];

    NSString *str2 = [NSString stringWithFormat:@"asdf"];

    NSComparisonResult result = [str1 compare:str2];

    NSLog(@"%ld", result);

 //9大小写转换

    NSString *str = [NSString stringWithFormat:@"lngfdknhHHO"];

    //(1)全部大写

    NSString *upperStr = str.uppercaseString;

    NSLog(@"%@", upperStr);

    //全部小写

    NSString *lowerStr = str.lowercaseString;

    NSLog(@"%@", lowerStr);

    //首字母大写

    NSString *capitalStr = str.capitalizedString;

    NSLog(@"%@", capitalStr);

//字符串与基本数值类型转换

    int a = 10;

    NSString *str = [NSString stringWithFormat:@"%d", a];

    NSLog(@"%@", str);

    

    int b = [str intValue];

    NSLog(@"%d", b);

//基本类型 --- NSNumber

    char num1 = 'a';

    NSNumber *newNum1 = [NSNumber numberWithChar:num1];

//NSNumber --- 基本类型

    NSNumber *nu = [NSNumber numberWithInt:23];

    int a = [nu intValue];