Object C 之字符串NSString

OC中,字符串是由unichar(Unicode)字符組成.

NSString:不可變字符串(創建以後,內容和長度不能更改).

NSMutableString:可變字符串(創建以後, 內容還可以修改).

//創建字符串對象

    //(1)初始化方法

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

    

    //(2)便利構造器

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

    //(3)將C語言的字符串轉化爲OC的字符串對象;

//    char cStr[] = "iphone";

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

//1字符串長度

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

    NSUInteger leng = str.length;

    NSLog(@"%lu", leng);

 //2判斷字符串是否是  http 開頭, 以png 結尾,如果是打印"這是一個有效連接",否則打印"連接出錯";

    NSString *str = [NSString stringWithFormat:@"http://www.baidu.com/picture/yuzhenluozhao.png"];

    //hasPrefix :判斷字符串是否以某個字符串開頭,返回值是bool類型

    //hasPrefix : 判斷字符串是否以某個字符串結尾,返回值是bool類型

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

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

    if (isPrefix && isSuffix) {

        NSLog(@"");

    }

//3判斷字符串是否相等

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

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

    //判斷地址

    if (str1 == str2) {

        NSLog(@"兩個對象地址相等");

    } else {

        NSLog(@"兩個對象地址不同");

    }

    //4判斷內容

    if ([str2 isEqualToString:str1]) {

        NSLog(@"兩個字符串內容相同");

    } else {

        NSLog(@"兩個字符串內容不同");

    }

 //5獲取子串

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

    //獲取keep

    NSString *keepString = [string substringToIndex:4];

    NSLog(@"%@", keepString);

    //獲取calm

    NSString *calmString = [string substringFromIndex:4];

    NSLog(@"%@", calmString);

    //獲取pca

//    NSMakeRange(NSUInteger loc, NSUInteger len)  快速創建 NSRange 類型的結構體變量

    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字符串替換

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

    //將a 換成aaa

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

    NSLog(@"%@", newStr);

//8比較字符串

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

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

    NSComparisonResult result = [str1 compare:str2];

    NSLog(@"%ld", result);

 //9大小寫轉換

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

    //(1)全部大寫

    NSString *upperStr = str.uppercaseString;

    NSLog(@"%@", upperStr);

    //全部小寫

    NSString *lowerStr = str.lowercaseString;

    NSLog(@"%@", lowerStr);

    //首字母大寫

    NSString *capitalStr = str.capitalizedString;

    NSLog(@"%@", capitalStr);

//字符串與基本數值類型轉換

    int a = 10;

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

    NSLog(@"%@", str);

    

    int b = [str intValue];

    NSLog(@"%d", b);

//基本類型 --- NSNumber

    char num1 = 'a';

    NSNumber *newNum1 = [NSNumber numberWithChar:num1];

//NSNumber --- 基本類型

    NSNumber *nu = [NSNumber numberWithInt:23];

    int a = [nu intValue];