warning: initialization from distinct Objective-c type (iPhone Development)

This warning is raised by Xcode whenever an implicit or INCORRECT type cast is occurring.
(The AS3 equivilant is the error: Error # 1067: Implicit coercion of a value of type * to an unrelated type *.)

"Distinct Objective-C type" is the type id. Apple docs say, "In Objective-C, object identifiers are a distinct data type: id. This type is defined as a pointer to an object..."

Example Causes:
NSMutableArray* myArraySorted = [myArray sortedArrayUsingSelector:@selector(compare:)];

The above will raise "warning: initialization from distinct Objective-c type" because sortedArrayUsingSelector returns an object of type id. We can correct this by simply casting the return value to the type NSMutableArray* as follows.

NSMutableArray* myArraySorted = (NSMutableArray*)[myArray sortedArrayUsingSelector:@selector(compare:)];

Finally notice that the incorrect cast that follows will also raise this warning:
NSMutableArray* myArraySorted = (NSString*)[myArray sortedArrayUsingSelector:@selector(compare:)];
Hence, whenever you see: "warning: initialization from distinct Objective-c type" you are performing an implicit cast.

MD5 hash on iPhone with cocoa and Objective-C

In beta 7 OpenSSL has been removed from the iPhone SDK. However, MD5 is still available.

Simply import CommonCrypto as follows:
#import < CommonCrypto/CommonDigest.h >

Then add this C function to your objective-c class between the @implementation and @end statements (if you like).

NSString* md5( NSString *str )
{
const char *cStr = [str UTF8String];
unsigned char result[CC_MD5_DIGEST_LENGTH];
CC_MD5( cStr, strlen(cStr), result );
return [NSString stringWithFormat:
@"%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X",
result[0], result[1], result[2], result[3], result[4], result[5], result[6], result[7],
result[8], result[9], result[10], result[11], result[12], result[13], result[14], result[15]
];
}

I am sure you can just use NSData for this but this is the way an example was posted on apple forums. Please feel free to add an NSData based solution.

Read the post here "http://discussions.apple.com/thread.jspa?threadID=1509152&tstart=96"