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class method

Enumerator.new

[unchecked out E, out R = void] (?::Integer arg0) { (::Enumerator::Yielder arg0) -> R } -> ::Enumerator[E, R]

Enumerator.new(size = nil) {|yielder| ... }

static VALUE
enumerator_initialize(int argc, VALUE *argv, VALUE obj)
{
    VALUE iter = rb_block_proc();
    VALUE recv = generator_init(generator_allocate(rb_cGenerator), iter);
    VALUE arg0 = rb_check_arity(argc, 0, 1) ? argv[0] : Qnil;
    VALUE size = convert_to_feasible_size_value(arg0);

    return enumerator_init(obj, recv, sym_each, 0, 0, 0, size, false);
}

Returns a new Enumerator object that can be used for iteration.

The given block defines the iteration; it is called with a “yielder” object that can yield an object via a call to method yielder.yield:

Example

fib = Enumerator.new do |yielder|
  n = next_n = 1
  while true do
    yielder.yield(n)
    n, next_n = next_n, n + next_n
  end
end

fib.take(10) # => [1, 1, 2, 3, 5, 8, 13, 21, 34, 55]

Parameter size specifies how the size is to be calculated (see size); it can either be a value or a callable object:

Example

Enumerator.new{}.size          # => nil
Enumerator.new(42){}.size      # => 42
Enumerator.new(-> {42}){}.size # => 42

See also .produce .product also in 4.0 · 3.4 · 3.3 · 3.2 · 3.1 · 3.0

next ›.produce