I have a method, where I want to use keyword parameter(s) and case/when statements, where I prefered to use symbols:
def navigate_to(page:)
case page
when :inbox
# some code
when :archive
# some code
else
# some code
end
end
Is this the correct syntax when calling the method?
navigate_to page: :inbox
The : : seems a little bit strange.
The keyword argument syntax is:
key: value
If key is page and value is the symbol :inbox, you indeed have:
page: :inbox
You could also use a positional argument instead:
def navigate_to(page)
# same as your code
end
navigate_to :inbox
Yes, the correct syntax is navigate_to page: :inbox.
While this is common Ruby, it is short and equivalent for several different things. First, the braces.
You are actually calling:
navigate_to(page: :inbox)
Second, the keyword argument pattern originates from hashes as arguments. Before there were keyword arguments, a common way would be to pass in a hash[1], like so:
def navigate_to(options)
page = options[:page]
end
navigate_to({ page: :inbox })
But when last argument in a method call is a hash, one can leave out the {}.
And last, the actual keys in the hash. A while ago (1.8 -> 1.9 IIRC) a short version was introduced for the following:
{ :page => 'Some Value' }, namely { page: 'Some Value' }. When Some Value is a symbol, that becomes { page: :inbox }.
So, taking all that:
navigate_to page: :inbox
Orignates from:
navigate_to({ :page => :inbox })
It might make more sense reading it like this, or knowing it comes from that.
And I know Ruby, nor ruby-ist, like braces, (), as can be seen in the mindboggling DSL of for example rspec, but I can advise especially new developers, to add them. It often makes code better understandable.
navigate_to(page: :inbox) is probably easier to understand than navigate_to page: :inbox, especially when you start calling through other methods: navigate_to page page_from_session :user.
[1] But, to stress, that is not really what is happening here. Keyword arguments and hash arguments do differ, now that we have keyword arguments. this just shows why the syntax is this way.