I can’t seem to pass an anonymous function as an option to a Plug. I am using plug_hmouse which from the documentation takes an option digest that is a function to be called on a string. The example is provided below: plug PlugHMouse, ... # other options digest: fn string -> Base.encode16(strin…

Module attributes can not contain anonymous functions. They may only contain a very strict subset of values. Whereas &Mod.fun/arit is one of these. &self().encode16lower/1 self() does not return a module name, but a PID. Probably you meant __MODULE__.encode16lower/1?

Thanks NobbZ, the __MODULE__ tip fixed the error! I didn’t realise that calling plug would create a module attribute. For anyone reading this thread in future, the docs on Module attributes actually have some info on this.

I don’t really understand this. Having this same issue, not sure how to go about solving it. I want to be able to dynamically define redirect behaviour. What do you mean about the module attributes? I have this plug: @moduledoc """ Redirects the path to one location or another depending on han…

The issue is that Plug pre-compiles the stack of plugs, so the init function is called at compile time and its result is stored in the compiled module. As the error message states, that place can’t store anonymous functions. The “standard idiom” for this situation is to use a tuple to specify a fu…

[image] al2o3cr: The “standard idiom” for this situation is to use a tuple to specify a function by name (you’ll see the term “MFA tuple” a lot). Something like: Why can’t it store anonymous functions? Also, is ther a reason to prefer an MFA tuple over referencing the named function directl…

[image] budgie: is ther a reason to prefer an MFA tuple over referencing the named function directly as in &SomeModule.some_fun/1? The ability to include extra arguments

Can’t you already do that with the &SomeModule.other_fun(&1, other_arg) syntax for a function that accepts 2 arguments? Or are you meaning something else?

&SomeModule.other_fun(&1, other_arg) is a shorthand for fn x -> SomeModule.other_fun(x, other_arg) end and will trigger precisely the same problems as any other anonymous function. Despite the similar notation, &SomeModule.other_fun/1 is represented differently internally.

Passing anonymous function as plug option

Questions & Help Questions

jswanner October 3, 2024, 4:04am 7

The ability to include extra arguments