Ruby transform string to method name

Question

To test image urls in a ruby project I can call a function as follows

validate_url("some_valid_url", "valid")
validate_url("inv#alid-url", "invalid")

The function looks like this:

def validate_url(image_url, state)
    assert state === 'valid' ? new_product(image_url).valid? : new_product(image_url).invalid?,
       "#{image_url} should always be " + state.upcase
end

is there a way to rewrite the line:

assert state === 'valid' ? new_product(image_url).valid? : new_product(image_url).invalid?

to something like

assert new_product(image_url).state.What-To-Do-Here?

which would then be equals to the following if state contains the string "valid"

assert new_product(image_url).valid?

can the new_product(image_url) return a state already? not sure I understood correctly: you method should return valid if URL is valid or "#{image_url} should always be " + state.upcase if it's invalid? - state being the argument that determining the validation of the URL? — Mshka
– Mshka, Commented Apr 8, 2021 at 11:53
I'd create a method that returns a boolean value instead of a string one valid_url?(image_url). — Yakov
– Yakov, Commented Apr 8, 2021 at 11:56
This seems weird to me. You already have validation methods, you already know which one to call, what's gained here? — Dave Newton
– Dave Newton, Commented Apr 8, 2021 at 12:42
@DaveNewton the gain is to not use the unnecessary if..else — caramba
– caramba, Commented Apr 8, 2021 at 12:45
In the code that calls this function you already have all the information needed--and you only need one of the "valid?"/"invalid?" methods becaise you can negate either's value. — Dave Newton
– Dave Newton, Commented Apr 8, 2021 at 12:53

caramba · Accepted Answer · 2021-04-08 12:42:19Z

2

You can do....

assert new_product(image_url).send(state + '?'), "#{image_url} should always be #{state.upcase}"

It would be prudent to ensure that state can only contain "valid" or "invalid"

edited Apr 8, 2021 at 12:42

caramba

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answered Apr 8, 2021 at 12:32

SteveTurczyn

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2 Comments

caramba Over a year ago

Thank you @Steve, after I figured out the 2 typos it did work :-)

Jörg W Mittag Over a year ago

There's no need to use send here. public_send should be enough.

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