字符串数值计算

//价格字符串转成NSDecimalNumber类型
NSDecimalNumber *objA = [NSDecimalNumber decimalNumberWithString:@"18.22"];
NSDecimalNumber *objB = [NSDecimalNumber decimalNumberWithString:@"2.30"];
//1、两个字符串相乘
NSDecimalNumber *objC = [objA decimalNumberByMultiplyingBy:objB];
//2、两个字符串相除
NSDecimalNumber *objD = [objA decimalNumberByDividingBy:objB];
//3、两个字符串相加
NSDecimalNumber *objE = [objA decimalNumberByAdding:objB];
//输出结果
NSLog(@"objC:%@,objD:%@",[objC stringValue],[objD stringValue]);

去除字符串两端的空格、用户连续输入换行过滤、字符串包含替换

//去除字符串两端的空格
NSString *textString = [self.userString.text stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];

//换行过滤
while ([textViewTextString containsString:@"\n\n"]) {
   textViewTextString  =  [textViewTextString stringByReplacingOccurrencesOfString:@"\n\n" withString:@"\n"];
}

//字符串包含替换
if ([pictureModel.picture_name containsString:@"200-200"]) {
   NSString *tempPictureName = [pictureModel.picture_name stringByReplacingOccurrencesOfString:@"200-200" withString:@"500-500"];
}

拼接字符串，可以增加空格

cell.detailTextLabel.text= [datamodel.day stringByAppendingFormat:@"            %@",datamodel.teacher];

字符串截取

NSString *a = @"abcde";
NSString *b = [a substringFromIndex:1];
NSLog(@"b--%@",b); //打印结果：bcde

NSString *c = [a substringToIndex:1];
NSLog(@"c--%@",c); //打印结果：a

//截取时间指定位置，2016年12月15日09:48:08  结果：09:48
NSString *cutTime = [stringTime substringWithRange:NSMakeRange(11,5)];

NSString中字符的位置

NSString *str = @"12345ba";
NSRange range = [str rangeOfString:@"a"];
NSLog(@"所查的字符坐标为：%ld",range.location);
//字符串位置为6

字符串中出现的某一个字符串次数

    int count = 0;
    NSString * string1 = @"1237847878712378798791231234";
    NSString * string2 = @"123";
    
    for (int i = 0; i < string1.length - string2.length + 1; i++) {
        if ([[string1 substringWithRange:NSMakeRange(i, string2.length)] isEqualToString:string2]) {
            count++;
            NSLog(@"count == %d",count);
        }
    }

获取字符串后缀名:详解讲解地址

NSString * urlString = @”http://www.baidu.com/img/10.gif”;
NSString *fileName = [urlString lastPathComponent]; //10.gif

手机号码隐藏中间位数（4位）

NSString *str = payModel.username;
self.username.text = [str stringByReplacingCharactersInRange:NSMakeRange(4, 4) withString:@"xxxx"];

字符串截取4位数 每4位后面加空格（1234567845235252）

NSString *newStr =@"1234567845235252";
NSMutableString *temp = [NSMutableString string];
for(int i =0; i < newStr.length; i++)
  {
     NSString *str = [newStr substringWithRange:NSMakeRange(i, 1)];
     [temp appendString:str];
     if ((i+1) % 4 == 0) {
         [temp appendString:@" "];
     }
}
//打印：1234 5678 4523 5252

字符串按多个符号分割，打印结果

NSString *str = @"abnfd,fdffds,fdsfsdf.dsds";
NSCharacterSet *set = [NSCharacterSet characterSetWithCharactersInString:@",."];
NSArray *tempArray = [str componentsSeparatedByCharactersInSet:set];
NSLog(@"%@",tempArray);

//判断字符串是否空值，添加到NSString扩展类中

+ (BOOL) isBlankString:(NSString *)string {
    //判断是否返回nil,返回（null）
    if (string == nil || string == NULL ||  [string isEqualToString:@"(null)"]) {
        return YES;
    }
    //判断是否返回为类
    if ([string isKindOfClass:[NSNull class]]) {
        return YES;
    }
    //判断是否返回空格
    if ([[string stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]] length]==0) {
        return YES;
    }
    return NO;
}

勤学如早春之苗，不见其增，日有所涨。
辍学如磨刀之石，不见其减，日有所损。