NSData 和数据类型间的转换

在做TCP数据传输中，协议往往需要传输的是Byte数组，而在iOS中我们常常都是发送的NSData类型，这时我们就需要转化。具体操作如下：

• Byte 转化为 NSData

Byte byte[] = {0x55, 0x07, 0x02, 0x01, 0x1A, 0x01, 0xAA};
NSData *data = [NSData dataWithBytes:byte lenght:7];

• NSData 转化为 Byte

NSString *testString = @"1234567890";　　
NSData *testData = [testString dataUsingEncoding: NSUTF8StringEncoding];　　
Byte *testByte = (Byte *)[testData bytes];

• int 转化为 NSData

int i = 1;
NSData *data = [NSData dataWithBytes:&i length: sizeof(i)];

• NSData 转化为 int

int k;
[data getBytes: &k length: sizeof(k)];
* NSData 转化为 NSString
NSString *aString = [[NSString alloc] initWithData:adata encoding:NSUTF8StringEncoding];

• NSString 转化为 NSData

NSString *aString = @"1234";
NSData *aData = [aString dataUsingEncoding: NSUTF8StringEncoding];

• NSData 转化为 NSString

char *str = "123456789";
 NSData *data = [NSData dataWithBytes:str length:strlen(str)];
 NSString *strN = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
 NSLog(@"%@",strN);

• UIImage 转化为 NSData

NSData *imageData = UIImagePNGRepresentation(image);

• NSData 转化为 UIImage

NSData *imageData = [NSData dataWithContentsOfFile: filePath];　　
UIImage *image = [UIImage imageWithData: imageData];