各种数据类型之间的转换

1. NSData－> NSString

NSString *aString 
 = [[NSString alloc] initWithData:adata encoding:NSUTF8StringEncoding];

2. NSString－>NSData

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

3. 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]);
}

4. 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];

7. 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];

8. UIImage－> NSData

UIImage *aimage = [UIImage imageWithData: imageData];