[erlang-questions] Asserting exact maps

[zxq9]

On 2017年10月11日 水曜日 18:20:20 zxq9 wrote:
> On 2017年10月11日 水曜日 08:47:40 Technion wrote:
> > Hi,
> > 
> > 
> > I'm wondering if there is a simple process I can use to verify a map
> > only contains valid variables.
>
> But I prefer the list version that operates over lists, personally.

... which I totally failed to provide any version of whatsoever.

A super simple one:

1> Checkmap =
1>     fun(Map, Keys) ->
1>         lists:sort(Keys) == lists:sort(maps:keys(Map)) 
1>     end.
#Fun<erl_eval.12.87737649>
2> Checkmap(#{"one" => 1, "two" => 2}, ["one", "two"]). 
true
3> Checkmap(#{"one" => 1, "two" => 2}, ["two", "one"]).
true
4> Checkmap(#{"one" => 1, "two" => 2}, ["two", "one", "three"]).
false
5> Checkmap(#{"one" => 1, "two" => 2}, ["two"]).                
false

Of course, here I am returning a boolean, but I prefer that for assertions
because I can do:

true = checkmap(Map, Keys)

and move on -- and reuse that function somewhere else in a non-crashing
way if I need to.

-Craig