CharlesO
I’m looking to improve this pattern.
It is a pattern I use in a lot of my projects.
defmodule Handler do
def handle_request(data) do
response = apply(@some_module_from_config, :parse, [data])
# do_something_with_response(response)
...
end
end
I then have customer specific implementations of :parse in separate modules, for example
defmodule CustomerA do
def parse(data) do
# specific parsing of this data for Customer-A
end
end
defmodule CustomerB do
def parse(data) do
# specific parsing of this data for Customer-B
end
end
This works, but can it be improved?
Is there a benefit for example to have a @behaviour in Handler which defines :parse and other functions
Then each Customer module no implements use Handler
Please are their better patterns for doing this?
Thanks.
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D4no0
Nope, all you need is something like this:
If you don’t implement the specified callbacks you will get a compilation warning.
You can also have the variant with the default implementation:
I wouldn’t recommend using the variant with default implementation unless that is strictly required, as it makes the code harder to read.
Also Liked
al2o3cr
The major benefit is compile-time checking:
CustomerAsays@behaviour Handlerbut doesn’t supply callbacks with the correct arities, the compiler will complainAs a side bonus, libraries like
moxcan use that same behaviour for their definitions.Eiji
No need to use
applyas it’s much more useful if you have function name stored in variable.Not only it would not give you any benefit, but it would also be wrongly used.
In
Handlermodule you have to define callbacks and / or macrocallbacks. You use@behaviourattribute inCustomerAandCustomerBmodules. In this tiny example it’s not important at all, but in general you use this to make sure that all callbacks are implemented asElixirgives compilation warning otherwise.egze
I also recommend watching the keynote from José https://www.youtube.com/watch?v=agkXUp0hCW8
He goes into the topic what to use when.
Last Post!
D4no0
You can’t, the module that defines behavior whole point is to make sure that you are implementing the required functions, it’s up to you how you call them afterwards.
You can either use the pattern you are already using with
apply/3or you can call directly the function, as module names are just plain atoms:You could add some compile-time checks to ensure that the module you are calling has the behavior declared, but I don’t see a lot of value from that.