On 31 May 2012 04:37, Chris Muller <asqueaker@gmail.com> wrote:
Another flexible option could be to test it respondsTo: each attribute being used for comparison.
This works quite well, and preserves "dynamic-ness": instead of checking for class membership or set-of-class membership (#species), you're saying "things that speak the same protocol/language might be equal, but definitely not if they don't speak the same language". That would permit non-transparent proxies to be #= to the things they proxy, for instance. (I use non-transparent proxies quite a lot, for instance as a means of providing an immutable pointer (Ref) to something _apparently_ immutable, but which I can change willy nilly without affecting anything pointing to the Ref.) frank
On Wed, May 30, 2012 at 8:32 AM, Henrik Sperre Johansen <henrik.s.johansen@veloxit.no> wrote:
On 30.05.2012 15:02, Mariano Martinez Peck wrote:
On Wed, May 30, 2012 at 2:37 PM, Henrik Sperre Johansen <henrik.s.johansen@veloxit.no> wrote:
On 30.05.2012 14:05, Mariano Martinez Peck wrote:
Hi guys. I found a problem while working with FuelPreview where we store objects of the graph in a Set. While doing a collect, there was an error because an implementation of #= was assuming that the argument was of a certain shape. Of course, that should answer false instead. So I wrote this test to see all existing wrong implementations:
testAllClassesImplementSafeEqualsMethod "This tests that all classes in the system that implements #= do it in a way that they don't throw error when passing as an argument something different from expected. The correct behavior is that #= answers false."   | wrongClasses |   wrongClasses := IdentityDictionary  new.   ((SystemNavigation default allImplementorsOf: #=)       collect: [:each | each methodClass])       do: [:each |         | instance |         "Some classes like CompiledMethod override basicNew to throw an error.         In any case, the comparison will be false, so no problem"         [instance := each basicNew] on: Error do: [].         [instance = Object new]           on: Error           do: [: err | wrongClasses at: each put: err ]].   self assert: wrongClasses isEmpty
The result is: {Magnitude. WideCharacterSet. KMKeymap. MCMockDefinition. ScaledDecimal. MCSnapshot}
So, my I think we should change #= in those classes by adding:
  self == aKeymap     ifTrue: [ ^ true ].   self class = aKeymap class     ifFalse: [ ^ false ].
at the beginning of the #=
what do you think? Â if agree, I open an issue.
-- Mariano http://marianopeck.wordpress.com
I'd test against self species rather than self class, since it gives greater flexibility for user-defined instances to potentially = classes in the system.
In other word, #class has a very strict meaning which would hinder extensibility, #species less so.
Ok, I see. But the classes are only a few (five). So you recommend you use self species instead of self class even if we "analyze" those 5 classes to see if it is worth it or not (for example, we check if they do override #species or not) ?
Yes. The default implementation of #species in Object uses the class primitive directly, so there's no overhead.
The benefit is that I could write a custom MyMagnitude class, override species: species    ^Magnitude
and not have to override the base system Magnitude = implementation in order to compare with MyMagnitude instances and have a true result. In other words, using species in #= even if it's not needed, is setting a good example.
and btw...the automatic #hash and #= generator, shouldn't use #species rather then #classes to?
thanks
Yes, I've never used those :)
Cheers, Henry