Method: Weak::Map#update

Defined in:

lib/weak/map.rb

#update(*other_maps) {|key, old_value, new_value| ... } ⇒ self Also known as: merge!

Note:

Weak::Map does not test member equality with == or eql?. Instead, it always checks strict object equality, so that, e.g., different String keys are not considered equal, even if they may contain the same content.

Merges each of other_maps into self; returns self.

Each argument in other_maps must be either a Weak::Map, a Hash object or must be transformable to a Hash by calling each_hash on it.

With arguments and no block:

• Returns self, after the given maps are merged into it.
• The given maps are merged left to right.
• Each duplicate-key entry’s value overwrites the previous value.

Example:

map = Weak::Map.new
map[:foo] = 0
map[:bar] = 1

h1 = {baz: 3, bar: 4}
h2 = {bam: 5, baz: 6}
map.update(h1, h2)
# => #<Weak::Map {:foo=>0, :bar=>4, :baz=>6, :bam=>5}

With arguments and a block:

• Returns self, after the given maps are merged.
• The given maps are merged left to right.
• For each duplicate key:
  • Calls the block with the key and the old and new values.
  • The block’s return value becomes the new value for the entry.
• The block should only return values which are otherwise strongly referenced to ensure that the value is not immediately garbage-collected.

Example:

map = Weak::Map.new
map[:foo] = 0
map[:bar] = 1

h1 = {baz: 3, bar: 4}
h2 = {bam: 5, baz: 6}
map.update(h1, h2) { |key, old_value, new_value| old_value + new_value }
# => #<Weak::Map {:foo=>0, :bar=>5, :baz=>9, :bam=>5}

With no arguments:

• Returns self.
• The block, if given, is ignored.

Yields:

• (key, old_value, new_value) —

  If self already contains a value for a key, we yield the key, the old value from self and the new value from the given map and use the value returned from the block as the new value to be merged.

Yield Parameters:

• key (Object) —

  the conflicting key

• old_value (Object) —

  the existing value from self

• old_value (Object) —

  the new value from one of the given other_maps

# File 'lib/weak/map.rb', line 733

def update(*other_maps)
  if block_given?
    missing = Object.new

    other_maps.each do |map|
      _implicit(map).each_pair do |key, value|
        old_value = fetch(key, missing)
        value = yield(key, old_value, value) unless missing == old_value
        self[key] = value
      end
    end
  else
    other_maps.each do |map|
      _implicit(map).each_pair do |key, value|
        self[key] = value
      end
    end
  end

  self
end