Question

I have a class ‘Data’ that uses a getter to access some array. If the array is null, then I want Data to access the file, fill up the array, and then return the specific value.

Now here’s my question:

When creating getters and setters should you also use those same accessor properties as your way of accessing that array (in this case)? Or should you just access the array directly?

The problem I am having using the accessors from within the class is that I get infinite loops as the calling class looks for some info in Data.array, the getter finds the array null so goes to get it from the file, and that function ends up calling the getter again from within Data, array is once again null, and we’re stuck in an infinite loop.

EDIT:

So is there no official stance on this? I see the wisdom in not using Accessors with file access in them, but some of you are saying to always use accessors from within a class, and others are saying to never use accessors from with the class……………………………………..

Answer 1

I agree with krosenvold, and want to generalize his advice a bit:

Do not use Property getters and setters for expensive operations, like reading a file or accessing the network. Use explicit function calls for the expensive operations.

Generally, users of the class will not expect that a simple property retrieval or assignment may take a lot of time.

This is also recommended in Microsoft’s Framework Design Guidelines.;

Do use a method, rather than a property, in the following situations.

The operation is orders of magnitude slower than a field set would be. If you are even considering providing an asynchronous version of an operation to avoid blocking the thread, it is very likely that the operation is too expensive to be a property. In particular, operations that access the network or the file system (other than once for initialization) should most likely be methods, not properties.