Objc-C 知識點回顧 四 NSString 、NSMutableString

Objc-C 知識點回顧 四 NSString 、NSMutableString

1.NSString
    //NSString:不可變字符串, 一旦創建, 不能修改
    //初始化方法
    //創建空字符串
    NSString *string1 = [[NSString alloc] init];
    NSLog(@"%@", string1);
     //根據給定的常量字符串,創建NSString對象
    NSString *string2 = [[NSString alloc] initWithString:@"iPhone"];
    NSLog(@"%@", string2);
     //常量區字符串
    NSString *string3 = @"iPhone";
    NSLog(@"%@", string3);
    NSLog(@"%p", string3);//輸出地址
    //如果要創建的字符串中出現其他變量, 需要用initWithFormat的方式創建
    NSInteger version = 6;
    NSString *string4 = [[NSString alloc] initWithFormat:@"iPhone %ld", version];
    NSLog(@"%@", string4);
   
   //便利構造器
    NSString *str1 = [NSString string];
    NSLog(@"%@", str1);
    NSString *str2 = [NSString stringWithString:@"iOS"];
    NSLog(@"%@", str2);
     NSString *str3 = @"iOS";
    NSLog(@"%@", str3);
    NSString *str4 = [NSString stringWithFormat:@"iOS %ld", version];
    NSLog(@"%@", str4);
    //獲取字符串的長度
//    NSUInteger length = [str4 length];//調用getter方法
//    NSLog(@"%lu", length);
    NSLog(@"%lu", str4.length);//點語法
    //判斷字符串是否以置頂字符串開始或結束
    NSString *str5 = @"abcdpp123";//常量區字符串
    NSString *str6 = [[NSString alloc] initWithFormat:@"abcdpp123"];//堆區字符串
    //前綴
    BOOL result = [str6 hasPrefix:@"abd"];
    NSLog(@"%d", result);
    //後綴
    result = [str6 hasSuffix:@"23"];
    NSLog(@"%d", result);
    //字符串截取(截取子字符串)
    //獲取abc(開頭字符串)
    NSString *subStr1 = [str6 substringToIndex:3];
    NSLog(@"%@", subStr1);
    //獲取123(結尾字符串)
    NSString *subStr2 = [str6 substringFromIndex:6];
    NSLog(@"%@", subStr2);
    //獲取dpp(中間字符串)
    //NSRange range = {3, 3};
    NSString *subStr3 = [str6 substringWithRange:NSMakeRange(3, 3)];
    NSLog(@"%@", subStr3);
    //拼接字符串
    NSString *newSubStr = [subStr1 stringByAppendingString:subStr2];
    NSLog(@"%@", subStr1);
    NSLog(@"%@", subStr2);
    NSLog(@"%@", newSubStr);
    NSLog(@"%p", newSubStr);//輸出地址
    NSString *newSubStr1 = [NSString stringWithFormat:@"%@%@", subStr1, subStr2];
    NSLog(@"%@", newSubStr1);
    NSLog(@"%p", newSubStr1);//輸出地址
    //替換字符串
    //@"NBA" -> @"CBA";
    NSString *str7 = @"NBANNN";
    NSString *newSubStr2 = [str7 stringByReplacingOccurrencesOfString:@"N" withString:@"C"];
    NSLog(@"%@", newSubStr2)
    //字符串比較
    //@"NBA" 和 @"CBA";
//    NSString *str8 = @"NBA";
//    NSString *str9 = @"CBA";
    NSString *str8 = [[NSString alloc] initWithFormat:@"NBA123456aa"];
    NSString *str9 = [[NSString alloc] initWithFormat:@"NBA123456aa"];
    //isEqualToString比較的是字符串的內容
    if ([str8 isEqualToString:str9]) {
        NSLog(@"字符串相等");
    } else {
        NSLog(@"不一致");
    }
    //==比較兩個對象是否一致, 如果對象一致, 他們的內容一定一致
    if (str8 == str9) {
        NSLog(@"字符串相等");
    } else {
        NSLog(@"不一致");
    }
    //字符串和數值類型相互轉換
    //@"123"
    //轉化成數字, 遇到非數字即停止轉換
    NSString *str10 = @"123a456";
    int a = [str10 intValue];
    NSLog(@"%d", a);
    NSInteger b = [str10 integerValue];
    NSLog(@"%ld", b);
    //大小寫轉換操作
    //@"ios" -> @"iOS"
    NSString *str11 = @"ios";
    //全部大寫
    NSString *newStr = [str11 uppercaseString];
    NSLog(@"%@", newStr);
    //首字母大寫
    NSLog(@"%@", [str11 capitalizedString]);
    //全部小寫
    NSLog(@"%@", [str11 lowercaseString]);
2.NSMutableString:可變字符串
    //@"iPhone"
    //創建可變字符串, 容器大小是一個預期值, 一般寫為0, 讓系統自己根據內容大小分配空間
    NSMutableString *mString = [[NSMutableString alloc] initWithCapacity:0];
    NSLog(@"%@", mString);
    //添加字符串
    [mString appendString:@"iPhone"];
    NSLog(@"%@", mString);
    [mString appendFormat:@"iPhone %ld", version];;
    NSLog(@"%@", mString);
    //插入字符串
    [mString insertString:@" " atIndex:6];
    NSLog(@"%@", mString);
    //刪除字符串
    [mString deleteCharactersInRange:NSMakeRange(0, 7)];
    NSLog(@"%@", mString);
    //做個練習,給定一個圖片文件名，判斷字符串中是否以“png”結尾，如果是就替換成“jpg”，如果不是，就拼接”.jpg”。
    NSMutableString *name = [[NSMutableString alloc] initWithCapacity:0];
    [name appendString:@"藍鷗.png"];
    if ([name hasPrefix:@"png"]) {
        NSLog(@"以'png'結尾");
        [name replaceCharactersInRange:NSMakeRange(name.length - 3, 3) withString:@"jpg"];
    } else {
        NSLog(@"不以'png'結尾");
        [name appendString:@".jpg"];
    }
    NSLog(@"%@", name);