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I'm trying to write a method that acts as a setter and takes some extra arguments besides the assigned value. Silly example:
class WordGenerator
def []=(letter, position, allowed)
puts "#{letter}#{allowed ? ' now' : ' no longer'} allowed at #{position}"
end
def allow=(letter, position, allowed)
# ...
end
end
Writing it as an indexer works and I can call it like this:
gen = WordGenerator.new
gen['a', 1] = true
# or explicitly:
gen.[]=('a', 1, true)
But when I try any of the following, the interpreter complains:
gen.allow('a', 1) = false # syntax error
gen.allow=('a', 1, false) # syntax error
Why won't this work, am I missing the obvious?
611
these methods allow us to access a class's instance variable from outside the class. Getter methods are used to get the value of an instance variable while the setter methods are used to set the value of an instance variable of some class.
Accessors are a way to create getter and setter methods without explicitly defining them in a class. There are three types fo accessors in Ruby. attr_reader automatically generates a getter method for each given attribute. attr_writer automatically generates a setter method for each given attribute.
In the code you posted, *args simply indicates that the method accepts a variable number of arguments in an array called args . It could have been called anything you want (following the Ruby naming rules, of course).
It doesn't work because the parser doesn't allow it. An equals sign is allowed in expressions of the form identifier = expression, expression.identifier = expression (where identifier is \w+), expression[arguments] = expression and expression.[]= arguments and as part of a string or symbol or character literal (?=). That's it.
gen.send(:allow=, 'a', 1, false) would work, but at that point you could as well just give the method a name that doesn't include a =.
126
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