Debugging & Best Practices - Learn SpriteBuilder for iOS Game Development - page 471

{
__weak CCNode* _levelNode;
__weak CCPhysicsNode* _physicsNode;
__weak CCNode* _playerNode;
__weak CCNode* _backgroundNode;
__weak GameMenuLayer* _gameMenuLayer;
__weak GameMenuLayer* _popoverMenuLayer;
// Other ivars omitted for brevity...
}
A lot can go wrong here, and it's quite common to forget to assign the doc root var in
SpriteBuilder or to make a typo in the node's name. Or you might assign the doc root var
to the wrong node or in the wrong CCB file, or you might edit a node's name in the
Timeline rather than its name property. It is good style to verify the assumption that these
variables have to be non- nil after a given point during the initialization of the class.
For instance, the end of the loadLevelNamed: method in Listing 14-7 would be a
good place to assert that crucial ivars are non- nil .
Listing 14-7 . Asserting that specific ivars are non-nil after the level was loaded
-(void) loadLevelNamed:(NSString*)levelCCB
{
// Existing code omitted for brevity...
NSAssert1(_physicsNode, @"physics node not found in
level: %@", levelCCB);
NSAssert1(_backgroundNode, @"bg node not found in
level: %@", levelCCB);
NSAssert1(_playerNode, @"player node not found in
level: %@", levelCCB);
}
To test a pointer variable for being non- nil , it suffices to just write the ivar's name. In a
condition or assertion, writing _playerNode is equal to writing _playerNode != nil .
You can also use the same format strings as in NSLog ; however, with NSAssert being a
macro and not an actual C function, you have to use NSAssert1 through NSAssert5
to match the number of format-string parameters. In the preceding example, there's one
format-string parameter, levelCCB , so NSAssert1 needed to be used.