ios- 常见数据类型转换

1、NSDate转NSString

+ (NSString *)stringFromDate:(NSDate *)date  
{  
    //获取系统当前时间  
    NSDate *currentDate = [NSDate date];  
    //用于格式化NSDate对象  
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];  
    //设置格式：zzz表示时区  
    [dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss zzz"];  
    //NSDate转NSString  
    NSString *currentDateString = [dateFormatter stringFromDate:currentDate];  
    //输出currentDateString  
    NSLog(@"%@",currentDateString);  
    return currentDateString;  
}

2、NSString转NSDate

+ (NSDate *)dateFromString:(NSString *)string  
{  
    //需要转换的字符串  
    NSString *dateString = @"2015-06-26 08:08:08";  
    //设置转换格式  
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init] ;  
    [formatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];  
    //NSString转NSDate  
    NSDate *date=[formatter dateFromString:dateString];  
    return date;  
}

3、字典转json格式字符串：

- (NSString*)dictionaryToJson:(NSDictionary *)dic
{
    NSError *parseError = nil;
    NSData *jsonData = [NSJSONSerialization dataWithJSONObject:dic options:NSJSONWritingPrettyPrinted error:&parseError];

    return [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];  
}

4、json格式字符串转字典

- (NSDictionary *)dictionaryWithJsonString:(NSString *)jsonString {

    if (jsonString == nil) {

        return nil;

    }

    NSData *jsonData = [jsonString dataUsingEncoding:NSUTF8StringEncoding];

    NSError *err;

    NSDictionary *dic = [NSJSONSerialization JSONObjectWithData:jsonData

                                                        options:NSJSONReadingMutableContainers

                                                          error:&err];

    if(err) {

        NSLog(@"json解析失败：%@",err);

        return nil;

    }

    return dic;

}

6、字符串NSString转NSNumber

NSString * str = @"890909";

    // 
字符串转为NSInteger类型
    NSInteger num = [str 
integerValue];
    NSLog(@"%li",num);
    // 
字符串转为NSNumber对象类型
    NSNumber * nums = 
@(num);
    NSLog(@"******%@",nums);


NSString *str = @"120". 

    NSNumberFormatter *numberFormatter = [[NSNumberFormatter alloc] init];
    [numberFormatter setNumberStyle:NSNumberFormatterDecimalStyle];
    NSNumber *numTemp = [numberFormatter numberFromString:str];

简化写法
NSNumber * nums = @([str integerValue]);

7、NSNumber转字符串NSString

NSString *string = [NSString stringWithFormat:@"%d",ivalue];

8、获取字符串中的数字

     NSString *urlString = @"fafadfdas12.4fdfas45dfa";
    
//方法一
    NSScanner *scanner = [NSScanner scannerWithString:urlString];
    [scanner scanUpToCharactersFromSet:[NSCharacterSet decimalDigitCharacterSet] intoString:nil];
    
    double number;
    [scanner scanDouble:&number];
    NSString *num=[NSString stringWithFormat:@"%g",number];//12.4
    

   //方法二 
    NSCharacterSet* nonDigits =[[NSCharacterSet decimalDigitCharacterSet] invertedSet];
    int remainSecond =[[urlString stringByTrimmingCharactersInSet:nonDigits] intValue];
    NSLog(@" num %d ",remainSecond); //12