NSString、NSData、char* 類型之間的轉換

NSString轉化爲UNICODE String

NSString *fname ＝ @"Test";
char fnameStr[10];
memcpy(fnameStr, [fname cStringUsingEncoding:NSUnicodeStringEncoding], 2*([fname length]));

與strcpy相比，memcpy並不是遇到’\0’就結束，而是一定會拷貝完n個字節

NSString 轉化爲 char *

NSString *str＝ @"Test";
const char *a =[str UTF8String];

char * 轉化爲 NSString

NSString *str=[NSString stringWithCString  encoding:NSUTF8StringEncoding];

char * 轉化 NSData

方法一：

char * a = (char*)malloc(sizeof(byte)*16);
NSData *data = [NSData dataWithBytes: a   length:strlen(a)];

方法二：

//轉換爲NSString： 
- (id)initWithUTF8String:(const char *)bytes
//然後用NSString的
- (NSData *)dataUsingEncoding:(NSStringEncoding)encoding

NSData 轉化 char *

NSData data ；
char* a=[data bytes];

NSData 轉化 NSString

NSData* data;
NSString* aStr= ［NSString alloc] initWithData:data   encoding:NSASCIIStringEncoding];

NSString 轉化 NSData對象

NSData* xmlData = [@"testdata" dataUsingEncoding:NSUTF8StringEncoding];

NSString 轉化 NSURL

 //NSURL *url = [NSURL URLWithString:[str   stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding ]]; 
NSString *urlString=[@"http://www.google.com/search?client=safari&rls=en&q=搜索&ie=UTF-8&oe=UTF-8" stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];

#

NSURL 轉化 NSString
NSURL *url=[NSURL URLWithString:urlString];
NSString *s=[[url absoluteString] stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];

NSArray *arr = [urlStr componentsSeparatedByString:@"&"];
NSURL *url = [NSURL URLWithString:[[arr objectAtIndex:0] stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding ]];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
[request setHTTPMethod:@"POST"];

NSMutableArray *_array = [[NSMutableArray alloc] initWithCapacity:0]; 
for (int i = 1; i < [arr count]; ++i ){ 
NSString *str = [arr objectAtIndex:i]; 
[_array addObject:str]; 
} 
[_array componentsJoinedByString:@"&"]; 
NSData *data = [[_array componentsJoinedByString:@"&"] dataUsingEncoding: NSASCIIStringEncoding]; 
[request setHTTPBody:data];

很多時候軟件讀取的中文網頁編碼集是gb2312，所以顯示出來的是亂碼。這時需要將NSString文字編碼轉換

NSURL *url = [NSURL URLWithString:urlStr];
NSData *data = [NSData dataWithContentsOfURL:url];    
NSStringEncoding enc = CFStringConvertEncodingToNSStringEncoding(kCFStringEncodingGB_18030_2000);    
NSString *retStr = [[NSString alloc] initWithData:data encoding:enc];

原文地址