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Ways a Method Takes Arguments (1)

1. Argument is required

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class Writer
  def self.type(w)
    "#{w}"
  end
end

Writer.type      # >> ArgumentError
Writer.type("1") # >> "1"

2. Argument is optional

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class Writer
  def self.type(w = nil)
    "#{w}"
  end
end

Writer.type      # >> ""
Writer.type("1") # >> "1"

3. One argument is required while the other optional

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class Writer
  def self.type(w1, w2 = nil)
    "#{w1}#{w2}"
  end
end

Writer.type           # >> ArgumentError
Writer.type("1")      # >> "1"
Writer.type("1", "2") # >> "12"

4. Any number of arguments is ok

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class Writer
  def self.type(*w) # "*" is known as "splat" operator
    w.join('')
  end
end

Writer.type                # >> ""
Writer.type("1")           # >> "1"
Writer.type("1", "2", "3") # >> "123"

Say “hello” to the splat operator *, a greedy fellow that swallows up all arguments, from its position onwards, the assigned variable (w in the above example) becomes an array that contains all the captured arguments.

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def showme(*args)
  args
end

showme(1, 2, 3, 4) # >> [1, 2, 3, 4]

5. One argument is required while the rest are optional & can be any number

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class Writer
  def self.type(w1, *w) # again, we have the "*" (splat) operator
    "w1" + w.join("")
  end
end

Writer.type                # >> ArgumentError
Writer.type("1")           # >> "1"
Writer.type("1", "2", "3") # >> "123"

Posted by Ng Tze Yang ruby, tips

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