Exclude properties from being considered regarding equality

[amyworrall]

Suppose I have some properties that hold cached data — stuff that can be derived but at a time penalty, so I'm cacheing it in the model. I'd like to exclude such properties from equality calculations. Perhaps there should be a method +(NSSet*)keypathsToExcludeFromEquality that you can override to easily exclude them?

I love that object equality is handled for me by default. It'd be even better if it was customisable in this manner!

[dannygreg]

I like that idea quite a bit.

I would suggest hacking and sending a pull request, code is always better than a suggestion 😄

[amyworrall]

I'm playing with this and a few other additions in a project I'm working on. I'll see how well they stand up to use, and if they work OK I'll look into contributing.

[dannygreg]

Exactly the reason a pull request is always preferred.

I'm going to close this in the anticipation of a future pull request. Would love to see what you come up with!

[foo4u]

I know this just got closed, but if a pull request is going to be created, I suggest the method be made inverse. Perhaps MTLModel can provide (NSSet *)propertyKeysForEquality that subclasses can override to remove elements that aren't desired for equality testing.

[jspahrsummers]

I think this should be handled with an application-level override of -isEqual:, since we could go on forever about all the different ways that people would like to override MTLModel's default behaviors. Subclassing and overriding works quite well, and generally reduces the complexity of the MTLModel interface.

Suppose I have some properties that hold cached data — stuff that can be derived but at a time penalty, so I'm cacheing it in the model. I'd like to exclude such properties from equality calculations.

In this particular case, it sounds like you would want to exclude those properties from most things, including copying and archiving. That can be done with a +propertyKeys override.