Question

I have a custom NSObject Class, lets call in People, and a Class from the CloudMade RMMarker.h called RMMarker. The RMMarker class has a property called data which is a NSObject. I know set the data by doing this:

People *aPeople = [[People alloc] init];   
marker.data = aPeople;

How can I read the data which is stored in data? All I know is its not

People *aPeople = [[People alloc] init];
aPeople = marker.data;

What is the right way to do so?

Thanks
Philip

Answer 1

Since you know that marker.data is of type People *, you can simply cast it to the correct type:

People *aPeople = (People *)marker.data;

Note that this will only work properly if marker.data is actually a People * object (or one of its subclasses). To be sure, you can add an assertion test:

People *aPeople = (People *)marker.data;
NSAssert([aPeople isKindOfClass:[People class]], "oops! Wrong type!");

For important details regarding the use of NSAssert(), please read: What are assertions or NSAssert good for in practice?