Hi,
I use macros for such requirement in my own code:
defmodule Constants do
defmacro val1 do
quote do
"val1"
end
end
defmacro val2 do
quote do
"val2"
end
endend
And here's how it's used:
defmodule Test do
require Constants
def match v do case v do
Constants.val1 -> "matched val1"
Constants.val2 -> "matched val2"
_ -> "no match"
end
endend
Max
On 22 May 2016 at 12:16, Nytz12 <[email protected]> wrote:
> Hi
>
> I use the following pattern to define cross module constants
>
> defmodule Visitor do
>
> defmodule FilterTypes do
> def c_GREATER_THAN, do: "greater_than"
> def c_LESS_THAN, do: "less_than"
> def c_IS, do: "is"
> def c_IS_NOT, do: "is_not"
> end
> ...
>
> Which lets me do something like this from other modules
>
> Visitor.FilterTypes.c_GREATER_THAN # == "greater than"
>
> Problem is that I just discored that these 'constants', which are really
> function calls, cannot be used to do pattern match like:
>
> def filter(query, filter, field, value) do
> case filter do
> FilterTypes.c_GREATER_THAN -> greater_than(query, field, value)
> FilterTypes.c_LESS_THAN -> less_than(query, field, value)
> FilterTypes.c_IS -> is(query, field, value)
> FilterTypes.c_IS_NOT -> is_not(query, field, value)
> _ -> {:error, "unknown filter", filter}
> end
> end
>
> Is there a better approach i'm missing?
>
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