Is there a way to make a method that can accept a parameter, but can also be called without one, in which case the parameter is regarded nil like the following?
some_func(variable)
some_func
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3 Answers
def some_func(variable = nil)
...
end
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7Then, of course, one has to somehow differentiate between default nil and explicit nil (if it matters) :) Commented Mar 2, 2016 at 13:00
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8That's what the
def some_func(variable = (variable_was_not_passed = true; nil))idiom is for. Commented Mar 2, 2016 at 19:51
Besides the more obvious option of parameters with default values, that Sawa has already shown, using arrays or hashes might be handy in some cases. Both solutions preserve nil as a an argument.
1. Receive as array:
def some_func(*args)
puts args.count
end
some_func("x", nil)
# 2
2. Send and receive as hash:
def some_func(**args)
puts args.count
end
some_func(a: "x", b: nil)
# 2
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what is the purpose of using
*argand**arginstead of justarg? Commented Mar 2, 2016 at 13:47 -
7@sagarpandya82
*argcollects the arguments as an array. Without the*you would have to callsome_func(["x", nil]).**argcollects all named arguments. Without the**it would only accept either a single unnamed argument, or any number of named arguments.– boglCommented Mar 2, 2016 at 14:07
You can also use a hash as argument and have more freedom:
def print_arg(args = {})
if args.has_key?(:age)
puts args[:age]
end
end
print_arg
# =>
print_arg(age: 35, weight: 90)
# => 35
