On Thu, May 31, 2012 at 5:37 AM, Chris Muller <asqueaker@gmail.com> wrote:
Another flexible option could be to test it respondsTo: each attribute being used for comparison.
Indeed, but on the other hand it could be slow ;)
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? 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
-- Mariano http://marianopeck.wordpress.com