NSString

目錄

    1.1 設置字符串行間距
    1.2 去除字符串前后的空格
    1.3 字符計算
    1.4 計算字符串高度
    1.5 null nil 轉 @""
    1.6 分割字符串
    1.7 字符串比較大小
    1.8 查找字符串位置
    1.9 判斷前后綴
    1.10 字符串提取
    1.12 保留小數點后兩位
    1.13 用0補全
    1.14 %處理方法
    1.15 "處理方法
    1.16 獲取圖片類型
    1.17 字符串的每一字符


1.1 設置字符串行間距

.h

+ (NSMutableAttributedString *)stringWithSpacing:(NSString *)string 
                                     LineSpacing:(int)num;


.m

+ (NSMutableAttributedString *)stringWithSpacing:(NSString *)string 
                                     LineSpacing:(int)num
{
//
    NSMutableAttributedString *attributedString = [[NSMutableAttributedString 
alloc] initWithString:string];

    NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle 
alloc] init];

   [paragraphStyle setLineSpacing:num];//調整行間距

   [attributedString addAttribute:NSParagraphStyleAttributeName 
value:paragraphStyle range:NSMakeRange(0, [string length])];

   return attributedString;

}


1.2 去除字符串前后的空格

.h

/**
* 去除字符串前后的空格，判斷輸入的內容不是空格
*
* @param string 傳入需要設置的字符串
*
* @return 去除空格后的字符串
*/

.h

+ (NSString *)stringWithTrimming:(NSString *)string;

.m

+ (NSString *)stringWithTrimming:(NSString *)string
{
    //去除空格
     NSString *cleanString = [string stringByTrimmingCharactersInSet:
[NSCharacterSet whitespaceAndNewlineCharacterSet]];

    return cleanString;

}

1.3 字符計算

.h

/**
* 計算一個字符串相當于多少個字
*
* @param text 傳入的字符串
*
* @return 字符個數
*/

+ (NSUInteger)stringWithLength:(NSString *)text;


.m

+ (NSUInteger)stringWithLength:(NSString *)text
{

    NSUInteger asciiLength = 0;

    for (NSUInteger i = 0; i < text.length; i++) {

         unichar uc = [text characterAtIndex: i];
         asciiLength += isascii(uc) ? 1 : 2;
    }

    NSUInteger unicodeLength = asciiLength / 2;

    if(asciiLength % 2) {

          unicodeLength++;

     }
     return unicodeLength;
}

1.4 計算字符串高度

.h

/**
* 計算字符串高度
*
* @param string 需要計算的字符串
* @param font label設置的字大小
* @param width 需要計算內容的寬度
*
* @return CGSize類型
*/

.h

+ (CGSize)stringWithHeight:(NSString *)string 
                  withFont:(UIFont *)font
                 withWidth:(CGFloat)width;

.m

+ (CGSize)stringWithHeight:(NSString *)string 
                  withFont:(UIFont *)font 
                 withWidth:(CGFloat)width 
{

    CGSize textBlockMinSize = CGSizeMake(width, 10000);

    CGSize size = CGSizeZero;
    NSStringDrawingOptions options = NSStringDrawingTruncatesLastVisibleLine
                                   | NSStringDrawingUsesLineFragmentOrigin
                                   | NSStringDrawingUsesFontLeading;

    NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle 
  alloc] init];

    [paragraphStyle setLineSpacing:1];//調整行間距

    NSDictionary *attributes = [NSDictionary dictionaryWithObjectsAndKeys:
font,NSFontAttributeName,paragraphStyle,NSParagraphStyleAttributeName, nil];

    size = [string boundingRectWithSize:textBlockMinSize 
                                options:options 
                             attributes:attributes
                                context:nil].size;

    return CGSizeMake(ceilf(size.width), ceilf(size.height));

}


1.5 null nil 轉  @""

.h

+ (NSString*)stringWithNull:(NSString *)string;

.m

// 轉換空串
+(NSString*)stringWithNull:(NSString *)string{

    if ([string isEqual:[NSNull null]]) {

        return @"";

    }else if ([string isKindOfClass:[NSNull class]]){

        return @"";

    }else if (string==nil){

        return @"";

    }
    return string;
}



1.6 分割字符串

//用空格分割

    NSString *string=@"i am a person";
    
    NSArray *array=[string componentsSeparatedByString:@" "];
    
    
    //多符號切割
    
    NSString *str=@"1(333·)333 3333";
    
    NSArray *arr=[str componentsSeparatedByCharactersInSet:[NSCharacterSet 
                 characterSetWithCharactersInString:@"()· "]];
 

1.7 字符串比較大小

//字符串會一個字符一個字符比較，返回類型1 0 -1

1 表示string1 大于 string2

0 表示string1 等于 string2

-1 表示string1 小于 string2



例1：@"9"大于@"75"

NSString *string1 = @"9";

NSString *string2 = @"75";

int result = [string1 compare:string2];

NSLog(@"%d",result);//返回值是整形：1



例2：@"72"小于@"75"

NSString *string1 = @"72";

NSString *string2 = @"75";

int result = [string1 compare:string2];

NSLog(@"%d",result);//返回值是整形：-1



例3：@"8"等于@"8"

NSString *string1 = @"8";

NSString *string2 = @"8";

int result = [string1 compare:string2];

NSLog(@"%d",result);//返回值是整形：0



例4：不區分大小寫比較

NSString *string1 = @"a";

NSString *string2 = @"A";

int result = [string1 compare:string2 options:NSCaseInsensitiveSearch]; 

NSLog(@"%d",result); //返回值是整形：0

1.8 查找字符串位置

NSString *str = @"lemon";

NSRange range = [str rangeOfString:@"em"];

NSLog(@"location = %lu, length = %lu",range.location,range.length);

1.9 判斷前后綴

//1.前綴
NSString *str = @"http://www.baidu.com";

BOOL isHave = [str hasPrefix:@"http://"];

NSLog(@"%d",isHave);


//2.后綴
NSString *str = @"http://www.baidu.com";

BOOL isHave = [str hasSuffix:@"com"];

NSLog(@"%d",isHave);


1.10 字符串提取

//例1：從0開始，到第5個
NSString *str = @"http://www.baidu.com";

NSString *topStr = [str substringToIndex:5];

NSLog(@"%@",topStr); 

http:


//例2：從第5個到最后一個
NSString *str = @"http://www.baidu.com";

NSString *endStr = [str substringFromIndex:5];

NSLog(@"%@",endStr);

//www.baidu.com


//例3：從第2個到第7個
NSString *str = @"http://www.baidu.com";

NSString *rangeStr = [str substringWithRange:NSMakeRange(2, 7)];

NSLog(@"%@",rangeStr);

tp://ww


1.11 UTF8轉碼

NSString* str = [str stringByAddingPercentEscapesUsingEncoding:
NSUTF8StringEncoding];


1.12 保留小數點后兩位

NSString *string = [NSString stringWithFormat:@"%.2f",M_PI];

//輸出結果是: 3.14

NSLog(@"%@", string);

1.13 用0補全

NSInteger count = 5;

//02代表:如果count不足2位 用0在最前面補全(2代表總輸出的個數)

NSString *string = [NSString stringWithFormat:@"%02zd",count];

//輸出結果是: 05

NSLog(@"%@", string);

1.14 %處理方法

NSInteger count = 50;

//%是一個特殊符號 如果在NSString中用到%需要如下寫法
NSString *string = [NSString stringWithFormat:@"%zd%%",count];

//輸出結果是: 50%
NSLog(@"%@", string);

1.15 "處理方法

NSInteger count = 50;

//"是一個特殊符號, 如果在NSString中用到"需要用\進行轉義

NSString *string = [NSString stringWithFormat:@"%zd\"",count];

//輸出結果是: 50"

NSLog(@"%@", string);

1.16 獲取圖片類型

- (NSString *)contentTypeForImageData:(NSData *)data {

     uint8_t c;

     [data getBytes:&c length:1];

    switch (c) {

        case 0xFF:

        return @"jpeg";

        case 0x89:

        return @"png";

        case 0x47:

        return @"gif";

        case 0x49:

        case 0x4D:

        return @"tiff";

        case 0x52:

        if ([data length] < 12) {

            return nil;

        }

        NSString *testString = [[NSString alloc] initWithData:
        [data subdataWithRange:NSMakeRange(0, 12)] 
        encoding:NSASCIIStringEncoding];

        if ([testString hasPrefix:@"RIFF"] && [testString 
      hasSuffix:@"WEBP"]) 
        {
              return @"webp";
        }

        return nil;

    }

    return nil;

}

1.17 獲取字符串的每一字符

- (NSArray *)words:(NSString *)string;
{

#if ! __has_feature(objc_arc)

NSMutableArray *words = [[[NSMutableArray alloc] init] autorelease];

#else

NSMutableArray *words = [[NSMutableArray alloc] init];

#endif

    const char *str = [string       cStringUsingEncoding:NSUTF8StringEncoding];

    char *word;

    for (int i = 0; i < strlen(str);) {

        int len = 0;

        if (str[i] >= 0xFFFFFFFC) {

            len = 6;

        } else if (str[i] >= 0xFFFFFFF8) {

           len = 5;

        } else if (str[i] >= 0xFFFFFFF0) {

          len = 4;

        } else if (str[i] >= 0xFFFFFFE0) {

          len = 3;

        } else if (str[i] >= 0xFFFFFFC0) {

          len = 2;

        } else if (str[i] >= 0x00) {

            len = 1;

        }

        word = malloc(sizeof(char) * (len + 1));

        for (int j = 0; j < len; j++) {

            word[j] = str[j + i];

        }

        word[len] = '\0';

        i = i + len;

        NSString *oneWord = [NSString stringWithCString:word           encoding:NSUTF8StringEncoding];

         free(word);

        [words addObject:oneWord];

        }

    return words;

}
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