`-init` method is called from the caller's thread | CoreData Pitfall

NSOperation.md

Refresh: How to use NSOperation

Using NSOperation is easy, typically, it is used as below:

Create your own NSOperation subclass

@interface MyOperation : NSOperation
@end

@implementation MyOperation
- (id)init{}
- (void)start{// do you job here}
- (void)main{// or do your job here}
@end

Add NSOperation instance to NSOperationQueue

NSOperationQueue *myQueue = [[NSOperationQueue alloc] init];
MyOperation *myOperation = [[MyOperation alloc] init];  // Here is the point
[myQueue addOperation:myOperation];

Biggest Problem

Don't forget that your NSOperation object is created and initialized in the caller's thread. If you are using CoreData and put the instantiation of NSManagedObjectContext in the -init method, you're wrong. Because the -init method is called in the caller's thread which is not what you want.