Method: Weak::Map#merge

Defined in:

lib/weak/map.rb

#merge(*other_maps) {|key, old_value, new_value| ... } ⇒ Weak::Map

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.

Returns the new Weak::Map formed by merging each of other_maps into a copy of 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 a new Weak::Map, after the given maps are merged into a copy of self.
• 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.merge(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.merge(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 a copy of self.
• The block, if given, is ignored.

Parameters:

• a list of maps which should be merged into a copy of self

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

Returns:

• a new weak map containing the merged pairs

# File 'lib/weak/map.rb', line 582

def merge(*other_maps, &block)
  dup.merge!(*other_maps, &block)
end