Laurent
What is a good way to compare structs?
In some tests, we need to compare 2 structs between each other. However when we build
- the test struct: this is done manually
%{
data_actions: %{A, B}
}
- the core struct, we go through a
data_actions |> Map.from_struct() |> Enum.reduce( ...)
Since OTP 26, Maps aren’t ordered anymore (Taking Control of Map Sort Order in Elixir · The Phoenix Files) so the result is random (in the resulting struct, the data_actions have a random order).
Is there any way to compare a struct recursively, without considering the values order? What is the elixir way to do it clean?
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christhekeele
The == operator does not care about order when comparing maps. This applies for structs too.
%{key1: :equal, key2: :values} == %{key2: :values, key1: :equal}
#=> true
%{key1: :unequal, key2: :values} == %{key2: :values, key1: :equal}
#=> false
For tests, you can just assert map1 == map2 as you would expect.
benwilson512
Again, what is wrong with a simple map_a == map_b ?
cevado
just adding to that, if you’re talking about tests… if you pattern match you can just look for the stuff you care for in a particular test run… so that works
assert %{field: :i_care_for} = %MyStruct{field: :i_care_for, other_field: :dont_care_about}
hubertlepicki
can you give me some example of map comparison that is failing? It should not be failing even if the order of fields looks different for some reason.
stefan_z
Absolutely nothing 
== operator is the best way to do it. For some reason my brain went for a more complex approach 
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