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Instance Method Summary collapse

Instance Method Details

#Array(type = nil, &block) ⇒ Object

call-seq:

Array(class).new                                        -> array
class MyClass < Array(class); end
class MyClass < Array class do |elem| elem.isvalid end
class MyClass < Array {|elem| elem.respond_to?(:meth) }

Checked array classes are subclasses of #Array that are created using this Array() method. They provide two kinds of checking on values entered into the array:

  • class checking (using kind_of?)

  • calling a block to determine validity

When any value is entered into the Array, by any method, that doesn’t satisfy your checks, you’ll get a nice exception. Beware of catching this exception, as in some cases (flatten for instance) the operation has been completed before the new array value is checked and the exception raised.

Here’s a simple example:

int_array = Array(Integer).new
int_array << 4
int_array.concat [ 6, 8, 10 ]
int_array << "Oops"                 # This will raise an exception

Surprisingly, a call to Array() works even as a superclass in a new class definition:

class MyArray < Array(Integer)
    def my_meth()
        ...
    end
end

and you can even use both together. An exception is raised if the block returns false/nil:

class MyArray < Array(Integer) {|i|
        (0..5).include?(i)          # Value must be an integer from 0 to 5
    }
end
MyArray.new << 6                    # This will raise an exception

The parameter to Array is optional, which removes the class check. You can use this to implement type checking that’s all your own:

class MyArray < Array {|i|
        i.respond_to?(:+@) && i.respond_to(:to_i)
    }
    def my_meth()
    end
end

Note that these latter examples create two new classes, one from the call to the Array() method, and one that you declared. So you don’t need to worry about overriding the methods that perform the checking; super works as normal.

There is no way to specify an initial size or a default value.

The methods that are overridden in order to implement the checking are listed below. All documented types of parameter lists and blocks are supported.

  • new

  • Array.[] (constructor)

  • []=

  • <<

  • concat

  • fill

  • flatten!

  • replace

  • insert

  • collect!

  • map!

  • push



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# File 'lib/chattr.rb', line 81

def Array(type = nil, &block)
    Class.new(Array).class_eval <<-END
	    if (Class === type)
	        @@_valid_type = lambda{|o| o.kind_of?(type) && (!block || block.call(o)) }
	    else
	        @@_valid_type ||= (block || lambda{|o| true})
	    end

	    def self.new(*a, &b)
		r = super()	# Is this correct?
		if (a.size == 1 && a[0].class != Fixnum)
		    r.concat(a[0])
		elsif (b)
		    raise "Wrong number of parameters for Array.new" if a.size != 1
		    (0...a[0]).each{|i|
			v = b.call(i)
			raise "Illegal array member from block initializer: \#{v.inspect}" unless @@_valid_type.call(v)
			r[i] = v
		    }
		else
		    v = a[1] || nil
		    if (a[1])
			raise "Illegal array member initializer: \#{v.inspect}" unless @@_valid_type.call(v)
		    end
		    if (a.size > 0)
			(0...a[0]).each_index{|i|
			    r[i] = v
			}
		    end
		end
		r
	    end

	    def self.[](*a)
		r = self.new
		r.concat(a)
	    end

	    def []=(*args)
		element = args.last
		raise "Illegal array member assignment: \#{element.inspect}" unless @@_valid_type.call(element)
		super(*args)
	    end

	    def <<(element)
		raise "Illegal array member append: \#{element.inspect}" unless @@_valid_type.call(element)
		super(element)
	    end

	    def concat(other)
		other.each{|e|
		    raise "Illegal array member in concat: \#{e.inspect}" unless @@_valid_type.call(e)
		}
		super(other)
	    end

	    def fill(*a, &b)
		unless b
		    v = a.shift
		    raise "Illegal array value fill: \#{v.inspect}" unless @@_valid_type.call(v)
		    b = lambda{|i| v}
		end

		case a.size
		when 0	    # Fill all members:
		    self.each_index{|i|
			e = b.call(i)
			self[i] = e
		    }
		when 1	    # Fill start..end or using Range:
		    r = a[0]
		    r = (a[0]..self.size-1) unless r.kind_of?(Range)
		    r.each{|i|
			e = b.call(i)
			raise "Illegal array block fill: \#{e.inspect}" unless @@_valid_type.call(e)
			self[i] = e
		    }
		when 2
		    start = a[0]
		    a[0] = Range.new(start, start+a.pop)
		end
		self
	    end

	    def check_valid(operation)
		each{|e|
		    raise "Illegal array element: \#{e.inspect} after \#{operation}" unless @@_valid_type.call(e)
		}
	    end

	    def flatten!()
		saved = clone
		a = super
		begin
		    check_valid "flatten!"
		rescue
		    clear
		    concat saved
		    raise
		end
		a
	    end

	    def replace(a)
		saved = clone
		begin
		    clear
		    concat(a)
		rescue
		    clear   # Restore the value
		    concat saved
		    raise
		end
		self
	    end

	    def insert(*a)
		start = a.shift
		a.each{|e|
		    raise "Illegal array element insert: \#{e.inspect}" unless @@_valid_type.call(e)
		}
		super(start, *a)
	    end

	    def collect!
		each_with_index{|e, i|
		    v = yield(e)
		    raise "Illegal array element in collect!: \#{v.inspect}" unless @@_valid_type.call(v)
		    self[i] = v
		}
		self
	    end

	    def map!(&b)
		collect!(&b)
	    end

	    def push(*a)
		concat a
		self
	    end

            self
	END
end