<
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