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I'm trying to dynamically define functions that call through to another function that takes an options parameter:
class MyClass
["hour", "minute", "second"].each do |interval|
define_method "get_#{interval}" do |args|
some_helper(interval, args)
end
end
def some_helper(interval, options={})
# Do something, with arguments
end
end
I'd like to be able to call the different methods on MyClass in these two ways (with and without optional arguments):
mc = MyClass.new
mc.get_minute( :first_option => "foo", :second_option => "bar")
mc.get_minute # This fails with: warning: multiple values for a block parameter (0 for 1)
On the second call to minute, I see this warning:
warning: multiple values for a block parameter (0 for 1)
515
Functions with optional arguments offer more flexibility in how you can use them. You can call the function with or without the argument, and if there is no argument in the function call, then a default value is used.
To indicate optional arguments, Square brackets are commonly used, and can also be used to group parameters that must be specified together. To indicate required arguments, Angled brackets are commonly used, following the same grouping conventions as square brackets.
We can explicitly accept a block in a method by adding it as an argument using an ampersand parameter (usually called &block ). Since the block is now explicit, we can use the #call method directly on the resulting object instead of relying on yield .
You can define Python function optional arguments by specifying the name of an argument followed by a default value when you declare a function. You can also use the **kwargs method to accept a variable number of arguments in a function. To learn more about coding in Python, read our How to Learn Python guide .
The only change you need to make is to change args to *args. The * indicates that args will contain an array of optional arguments to the block.
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