iOS的NSString总结

NSString *astring = @"This is a String!";                             //固定字符串
NSString *str = [NSString stringWithFormat:@"asd%d%@",123,@"ttt"];    //拼组字符串

NSString *str = [@"asd" substringFromIndex:1];                       //从第几位开始截到最后
NSString *str1 = [str substringToIndex:1];                           //从开始位置截到第几位
NSString *str = [[@"asd" substringFromIndex:1] substringToIndex:1];  //从第几位开始截几个字符

NSArray *array = [@"asd|tes|mmm" componentsSeparatedByString:@"|"];

 NSRange range = [@"12rasd124" rangeOfString:@"asd"];
 if (range.location != NSNotFound) {
      NSString *str = [@"12rasd124" substringWithRange:range];
 }

NSString *str = [@"asdasd" stringByReplacingOccurrencesOfString:@"asd" withString:@"ok"];

[filepath lastPathComponent];                 //获得文件名
[filepath pathExtension];                     //获得文件扩展名
[filtpaht stringByDeletingLastPathComponent]; //获得文件的所在文件夹路径
[filtpath stringByDeletingPathExtension];     //获得去除扩展名的文件路径

if (str.lenght > 0) //不管str是不是nil都可以这么判断

if ([@"asd" isEqualToString:@"asd"]) {
   
}

    NSString *stra = @"asd";
    NSString *strb = @"dfs";
    NSComparisonResult result = [stra compare:strb];
    if (result == NSOrderedSame) {
        
    } else if (result == NSOrderedAscending) {
    
    } else {
        
    }

- (NSString *)md5HexDigest
{
    const char* str = [self UTF8String];
    unsigned char result[CC_MD5_DIGEST_LENGTH];
    CC_MD5(str, strlen(str), result);
    NSMutableString *ret = [NSMutableString stringWithCapacity:CC_MD5_DIGEST_LENGTH];
    
    for(int i = 0; i<CC_MD5_DIGEST_LENGTH; i++) {
        [ret appendFormat:@"%02X",result[i]];
    }
    return ret;
    
}

- (NSString *)stringEncode {
    NSString *encodedString = (NSString *)CFBridgingRelease(CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault, (CFStringRef)self, NULL, CFSTR(":/?#[]@!$ &'()*+,;=\"<>%{}|\\^~`"), kCFStringEncodingUTF8));
    return encodedString;
}

- (NSString *)stringDecode {
    NSString *result = [(NSString *)self stringByReplacingOccurrencesOfString:@"+" withString:@" "];
    result = [result stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
    return result;
}

- (CGSize)boundingRectWithSize:(CGSize)size
                  withTextFont:(UIFont *)font {
    if ([self isEqualToString:@""]) {
        return CGSizeMake(0, 0);
    }
    NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle alloc] init];
    paragraphStyle.lineBreakMode = NSLineBreakByWordWrapping;
    paragraphStyle.lineSpacing = 0;
    NSDictionary *attributes = @{NSFontAttributeName:font, NSParagraphStyleAttributeName:paragraphStyle.copy};
    
    return [self boundingRectWithSize:size options:NSStringDrawingUsesLineFragmentOrigin attributes:attributes context:nil].size;
}

- (BOOL)isEmail
{
    NSString *emailRegEx =  
    @"(?:[a-z0-9!#$%\\&'*+/=?\\^_`{|}~-]+(?:\\.[a-z0-9!#$%\\&'*+/=?\\^_`{|}"  
    @"~-]+)*|\"(?:[\\x01-\\x08\\x0b\\x0c\\x0e-\\x1f\\x21\\x23-\\x5b\\x5d-\\" 
    @"x7f]|\\\\[\\x01-\\x09\\x0b\\x0c\\x0e-\\x7f])*\")@(?:(?:[a-z0-9](?:[a-"  
    @"z0-9-]*[a-z0-9])?\\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?|\\[(?:(?:25[0-5"  
    @"]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-"  
    @"9][0-9]?|[a-z0-9-]*[a-z0-9]:(?:[\\x01-\\x08\\x0b\\x0c\\x0e-\\x1f\\x21"  
    @"-\\x5a\\x53-\\x7f]|\\\\[\\x01-\\x09\\x0b\\x0c\\x0e-\\x7f])+)\\])";  

    NSPredicate *regExPredicate = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", emailRegEx];  
    return [regExPredicate evaluateWithObject:[self lowercaseString]];  
}

- (NSString *)base64 {
    // Create NSData object
    NSData *nsdata = [self dataUsingEncoding:NSUTF8StringEncoding];
    
    // Get NSString from NSData object in Base64
    NSString *base64Encoded = [nsdata base64EncodedStringWithOptions:0];
    
    // Print the Base64 encoded string
    return base64Encoded;
}

- (NSString *)base64Decoded {
    // NSData from the Base64 encoded str
    NSData *nsdataFromBase64String = [[NSData alloc] initWithBase64EncodedString:self options:0];
    
    // Decoded NSString from the NSData
    NSString *base64Decoded = [[NSString alloc] initWithData:nsdataFromBase64String encoding:NSUTF8StringEncoding];
   
    return base64Decoded;
}