edge badge

The WatchStack keeps a stack of the modules being watched as files are loaded. If a file in the process of being loaded (parent.rb) triggers the load of another file (child.rb) the stack will ensure that child.rb handles the new constants.

If child.rb is being autoloaded, its constants will be added to autoloaded_constants. If it was being `require`d, they will be discarded.

This is handled by walking back up the watch stack and adding the constants found by child.rb to the list of original constants in parent.rb.

Methods
E
N
W
Included Modules
Class Public methods
new()

@watching is a stack of lists of constants being watched. For instance, if parent.rb is autoloaded, the stack will look like [[Object]]. If parent.rb then requires namespace/child.rb, the stack will look like [[Object], [Namespace]].

# File activesupport/lib/active_support/dependencies.rb, line 86
def initialize
  @watching = []
  @stack = Hash.new { |h,k| h[k] = [] }
end
Instance Public methods
each(&block)
# File activesupport/lib/active_support/dependencies.rb, line 91
def each(&block)
  @stack.each(&block)
end
new_constants()

Returns a list of new constants found since the last call to watch_namespaces.

# File activesupport/lib/active_support/dependencies.rb, line 101
def new_constants
  constants = []

  # Grab the list of namespaces that we're looking for new constants under
  @watching.last.each do |namespace|
    # Retrieve the constants that were present under the namespace when watch_namespaces
    # was originally called
    original_constants = @stack[namespace].last

    mod = Inflector.constantize(namespace) if Dependencies.qualified_const_defined?(namespace)
    next unless mod.is_a?(Module)

    # Get a list of the constants that were added
    new_constants = mod.local_constants - original_constants

    # self[namespace] returns an Array of the constants that are being evaluated
    # for that namespace. For instance, if parent.rb requires child.rb, the first
    # element of self[Object] will be an Array of the constants that were present
    # before parent.rb was required. The second element will be an Array of the
    # constants that were present before child.rb was required.
    @stack[namespace].each do |namespace_constants|
      namespace_constants.concat(new_constants)
    end

    # Normalize the list of new constants, and add them to the list we will return
    new_constants.each do |suffix|
      constants << ([namespace, suffix] - ["Object"]).join("::")
    end
  end
  constants
ensure
  # A call to new_constants is always called after a call to watch_namespaces
  pop_modules(@watching.pop)
end
watch_namespaces(namespaces)

Add a set of modules to the watch stack, remembering the initial constants.

# File activesupport/lib/active_support/dependencies.rb, line 138
def watch_namespaces(namespaces)
  @watching << namespaces.map do |namespace|
    module_name = Dependencies.to_constant_name(namespace)
    original_constants = Dependencies.qualified_const_defined?(module_name) ?
      Inflector.constantize(module_name).local_constants : []

    @stack[module_name] << original_constants
    module_name
  end
end
watching?()
# File activesupport/lib/active_support/dependencies.rb, line 95
def watching?
  !@watching.empty?
end