Objective-C NSString与char *互相转换

--UTF8String
const char *cString = [string UTF8String];

--cStringUsingEncoding:
const char *cString = [string cStringUsingEncoding:NSUTF8StringEncoding];

--getCString:maxLength:encoding:
char cStringPtr[string.length * 3 + 1];
memset(cStringPtr, 0, sizeof(cStringPtr));
[string getCString:cStringPtr maxLength:sizeof(cStringPtr) encoding:NSUTF8StringEncoding];

----initWithUTF8String:

NSString *string = [[NSString alloc] initWithUTF8String:cString];

----initWithCString:encoding:
NSString *string = [[NSString alloc] initWithCString:cString encoding:NSUTF8StringEncoding];