In Objective C, can you check if an object has a particular property or message?
Objective CObjective C Problem Overview
I wat to do something like this:
if (viewController.mapView) [viewController.mapView someMethod];
However, if mapView is not a class variable, this crashes. How do I check if mapView exists?
Objective C Solutions
Solution 1 - Objective C
For ordinary selectors, you can use respondsToSelector:. I'm not certain if this will work for new-style property access (as it appears you are using in this example). To test if a class responds to a given selector, use instancesRespondToSelector:.
Solution 2 - Objective C
Also, As Jason poninted out here, you can also use NSSelectorFromString to dynamically check at runtime. E.g.
if ([self respondsToSelector:NSSelectorFromString(elementName)])
{
[self setValue:elementInnerText forKey:elementName];
}
Solution 3 - Objective C
Oops, found it:
if ([vc respondsToSelector:@selector(mapView)]) {
[[vc mapView] viewWillAppear:YES];
}
Solution 4 - Objective C
Here is more than you asked for but a category I have found useful to generically handle NSObject properties:
http://www.whynotsometime.com/Why_Not_Sometime/Category_Enhancing_NSObject.html