简介:
1. NSData 与 NSString
NSData－> NSString
NSString *aString = [[NSString alloc] initWithData:adataencoding:NSUTF8StringEncoding];
NSString－>NSData
NSString *aString = @"1234abcd";
NSData *aData = [aString dataUsingEncoding: NSUTF8StringEncoding]; 

//将data类型的数据,转成UTF8的数据
+(NSString *)dataToUTF8String:(NSData *)data
{
 NSString *buf = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
 return [buf autorelease];
}

//将string转换为指定编码 
+(NSString *)changeDataToEncodinString:(NSData *)data encodin:(NSStringEncoding )encodin{
    NSString *buf = [[[NSString alloc] initWithData:data encoding:encodin] autorelease];
    return buf;
}

2. NSData 与 UIImage
NSData－>UIImage
UIImage *aimage = [UIImage imageWithData: imageData];
 
//例：从本地文件沙盒中取图片并转换为NSData
NSString *path = [[NSBundle mainBundle] bundlePath];
NSString *name = [NSString stringWithFormat:@"ceshi.png"];
NSString *finalPath = [path stringByAppendingPathComponent:name];
NSData *imageData = [NSData dataWithContentsOfFile: finalPath];
UIImage *aimage = [UIImage imageWithData: imageData];

3.NSData与NSArray  NSDictionary

+(NSString *)getLocalFilePath:(NSString *) fileName
{
 return [NSString stringWithFormat:@"%@/%@%@", NSHomeDirectory(),@“Documents”,fileName];
}

包括将NSData写进Documents目录
从Documents目录读取数据
在进行网络数据通信的时候，经常会遇到NSData类型的数据。在该数据是dictionary结构的情况下，系统没有提供现成的转换成NSDictionary的方法，为此可以通过Category对NSDictionary进行扩展，以支持从NSData到NSDictionary的转换。声明和实现如下：
 
+ (NSDictionary *)dictionaryWithContentsOfData:(NSData *)data {     
    CFPropertyListRef list = CFPropertyListCreateFromXMLData(kCFAllocatorDefault, (CFDataRef)data, kCFPropertyListImmutable, NULL);
    if(list == nil) return nil; 
    if ([(id)list isKindOfClass:[NSDictionary class]]) { 
         return [(NSDictionary *)list autorelease]; 
        } 
    else { 
         CFRelease(list); 
         return nil; 
        } 
}

NSDate

//函数作用 :date根据formatter转换成string
+(NSString*)dateToString:(NSString *)formatter date:(NSDate *)date
{
    NSDateFormatter *dateFormatter = [[[NSDateFormatter alloc] init] autorelease];
    [dateFormatter setDateFormat:formatter];
    return[dateFormatter stringFromDate:date];
}

//函数作用 :string类型的时间戳转换成时间
+(NSString*)dateStringToString:(NSString *)dateStr
{
    if ([dateStr isKindOfClass:[NSNull class]]) {
        return nil;
    }
    else{
        NSInteger time = [dateStr intValue];
        NSDate *date = [NSDate dateWithTimeIntervalSince1970:time];
        NSString *timestr = [NSString stringWithFormat:@"%@",date];
        NSRange rang;
        rang.location = 0;
        rang.length = 10;
        NSString *needtime = [timestr substringWithRange:rang];
        return needtime;
    }
}

//函数作用 :将日期从原格式转换成需要的格式
+(NSString*)convertDateFormatter:(NSString*)sourceFormatter 
                  targetFormatter:(NSString*)targetFormatter  
                       dateString:(NSString*)dateString
{   
    NSDateFormatter *dateFormatter = [[[NSDateFormatter alloc] init] autorelease];
    [dateFormatter setDateFormat:sourceFormatter];
    NSDate *date = [dateFormatter dateFromString:dateString];
    [dateFormatter setDateFormat:targetFormatter];
    return[dateFormatter stringFromDate:date];
}

//函数作用 :将日期字符串转换成date
+(NSDate *)stringToDate:(NSString *)formatter dateString:(NSString *)dateString{
 NSDateFormatter *dateFormatter= [[[NSDateFormatter alloc] init] autorelease];
 [dateFormatter setDateFormat:formatter];
 return [dateFormatter dateFromString:dateString];
}

//时间戳转换成时间
                NSInteger time = [[dic objectForKey:@"press_date"] intValue];
                NSDate *date = [NSDate dateWithTimeIntervalSince1970:time];
                NSString *timestr = [NSString stringWithFormat:@"%@",date];
                NSRange rang;
                rang.location = 0;
                rang.length = 10;
                NSString *needtime = [timestr substringWithRange:rang];

1. NSData 与 NSString

NSData－> NSString

NSString *aString = [[NSString alloc] initWithData:adataencoding:NSUTF8StringEncoding];

NSString－>NSData

NSString *aString = @"1234abcd";

NSData *aData = [aString dataUsingEncoding: NSUTF8StringEncoding];

2.NSData 与 Byte

NSData－> Byte数组

NSString *testString = @"1234567890";

NSData *testData = [testString dataUsingEncoding: NSUTF8StringEncoding];

Byte *testByte = (Byte *)[testData bytes];

for(int i=0;i<[testData length];i++)

printf("testByte = %d\n",testByte[i]);

Byte数组－> NSData

Byte byte[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23};

NSData *adata = [[NSData alloc] initWithBytes:byte length:24];

Byte数组－>16进制数

Byte *bytes = (Byte *)[aData bytes];

NSString *hexStr=@"";

for(int i=0;i<[encryData length];i++)

{

NSString *newHexStr = [NSString stringWithFormat:@"%x",bytes[i]&0xff];///16进制数

if([newHexStr length]==1)

hexStr = [NSString stringWithFormat:@"%@0%@",hexStr,newHexStr];

else 

hexStr = [NSString stringWithFormat:@"%@%@",hexStr,newHexStr];

}

NSLog(@"bytes 的16进制数为:%@",hexStr);

16进制数－>Byte数组

///// 将16进制数据转化成Byte 数组

NSString *hexString = @"3e435fab9c34891f"; //16进制字符串

int j=0;

Byte bytes[128];  ///3ds key的Byte 数组， 128位

for(int i=0;i<[hexString length];i++)

{

int int_ch;  /// 两位16进制数转化后的10进制数

unichar hex_char1 = [hexString characterAtIndex:i]; ////两位16进制数中的第一位(高位*16)

int int_ch1;

if(hex_char1 >= ‘0‘ && hex_char1 <=‘9‘)

int_ch1 = (hex_char1-48)*16;   //// 0 的Ascll - 48

else if(hex_char1 >= ‘A‘ && hex_char1 <=‘F‘)

int_ch1 = (hex_char1-55)*16; //// A 的Ascll - 65

else 

int_ch1 = (hex_char1-87)*16; //// a 的Ascll - 97

i++;

unichar hex_char2 = [hexString characterAtIndex:i]; ///两位16进制数中的第二位(低位)

int int_ch2;

if(hex_char2 >= ‘0‘ && hex_char2 <=‘9‘)

int_ch2 = (hex_char2-48); //// 0 的Ascll - 48

else if(hex_char1 >= ‘A‘ && hex_char1 <=‘F‘)

int_ch2 = hex_char2-55; //// A 的Ascll - 65

else 

int_ch2 = hex_char2-87; //// a 的Ascll - 97

int_ch = int_ch1+int_ch2;

NSLog(@"int_ch=%d",int_ch);

bytes[j] = int_ch;  ///将转化后的数放入Byte数组里

j++;

}

NSData *newData = [[NSData alloc] initWithBytes:bytes length:128];

NSLog(@"newData=%@",newData);

3. NSData 与 UIImage

NSData－>UIImage

UIImage *aimage = [UIImage imageWithData: imageData];

//例：从本地文件沙盒中取图片并转换为NSData

NSString *path = [[NSBundle mainBundle] bundlePath];

NSString *name = [NSString stringWithFormat:@"ceshi.png"];

NSString *finalPath = [path stringByAppendingPathComponent:name];

NSData *imageData = [NSData dataWithContentsOfFile: finalPath];

UIImage *aimage = [UIImage imageWithData: imageData];

UIImage－> NSData

NSData *imageData = UIImagePNGRepresentation(aimae); 

iOS 低位、高位字节转换为int