creating objects within a block

[myArray enumerateObje开发者_开发知识库ctsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
        [[myTreeNode mutableChildNodes] addObject:[NSTreeNode treeNodeWithRepresentedObject:obj]];
        //myTreeNode is an NSTreeNode
    }];

Is it ok to create objects from within a block?

Yes. It's basically OK to do anything in a block that you might do in a normal function.