学步园

一：NSString和NSURL 转换

//NSString->NSURL
NSString *urlString=[@"http://www.google.com" stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
NSURL *url=[NSURL URLWithString:urlString]; 
//NSURL->NSString 
NSString *urlString=[[url absoluteString] stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];

二：NSString和NSData转换（即可作json串互相转换）

//NSData－> NSString
NSString *testString = [[NSString alloc] initWithData:testData encoding:NSUTF8StringEncoding];
//NSString－>NSData
NSString *aString = @"我是NSString";
NSData *testData = [testString dataUsingEncoding: NSUTF8StringEncoding];

三：NSData和NSImage转换

//NSData－>UIImage
UIImage *testImage = [UIImage imageWithData: imageData];
//UIImage->NSData
NSData *imageData = UIImagePNGRepresentation(testImage)
//或者
NSData *imageData = UIImageJPEGRepresentation(testImage,1.0)

四：NSData和NSDictionary转换

//NSData-->NSDictionary
NSDictionary *testDict = [NSJSONSerialization JSONObjectWithData:testData options:NSJSONReadingMutableContainers error:nil]
//或者
NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:testData];  
NSDictionary *myDictionary = [[unarchiver decodeObjectForKey:@"Some Key Value"] retain];  
[unarchiver finishDecoding];
//NSDictionay --> NSData
NSMutableData *data = [[NSMutableData alloc] init];  
NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];  
[archiver encodeObject:params forKey:@"Some Key Value"];  
[archiver finishEncoding];

五：NSDictionary和JSON转换

//NSDictionary -> JSON:  //这个方法是SBJson类库里的，需要导入SBJson.h
NSString *jsonStr=[dict JSONRepresentation];
//建议（特别是http取回来的jsonStr转换如下）
//JSON->NSDictionary:
NSData *jsonData = [testJsonStr dataUsingEncoding:NSUTF8StringEncoding];
NSDictionary *dict = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingMutableContainers error:nil]

//摘录其他同学的

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];