method

detect

v2_6_3 - Show latest stable - Class: Enumerable

detect(*args)

public

Passes each entry in enum to block. Returns the first for which block is not false. If no object matches, calls ifnone and returns its result when it is specified, or returns nil otherwise.

If no block is given, an enumerator is returned instead.

(1..100).detect  #=> #<Enumerator: 1..100:detect>
(1..100).find    #=> #<Enumerator: 1..100:find>

(1..10).detect   { |i| i % 5 == 0 and i % 7 == 0 }   #=> nil
(1..10).find     { |i| i % 5 == 0 and i % 7 == 0 }   #=> nil
(1..100).detect  { |i| i % 5 == 0 and i % 7 == 0 }   #=> 35
(1..100).find    { |i| i % 5 == 0 and i % 7 == 0 }   #=> 35

static VALUE
enum_find(int argc, VALUE *argv, VALUE obj)
{
    struct MEMO *memo;
    VALUE if_none;

    if_none = rb_check_arity(argc, 0, 1) ? argv[0] : Qnil;
    RETURN_ENUMERATOR(obj, argc, argv);
    memo = MEMO_NEW(Qundef, 0, 0);
    rb_block_call(obj, id_each, 0, 0, find_i, (VALUE)memo);
    if (memo->u3.cnt) {
        return memo->v1;
    }
    if (!NIL_P(if_none)) {
        return rb_funcallv(if_none, id_call, 0, 0);
    }
    return Qnil;
}

1Note

Optional Argument for detect/find [Not Documented]

Alex · Aug 15, 20088 thanks

detect/find’s optional argument lets you specify a proc or lambda whose return value will be the result in cases where no object in the collection matches the criteria.

classic_rock_bands = ["AC/DC", "Black Sabbath","Queen", "Ted Nugent and the Amboy Dukes","Scorpions", "Van Halen"]
default_band = Proc.new {"ABBA"}
classic_rock_bands.find(default_band) {|band| band > "Van Halen"}
=> "ABBA"

or random_band = lambda do fallback_bands = ["Britney Spears", "Christina Aguilera", "Ashlee Simpson"] fallback_bands[rand(fallback_bands.size)] end classic_rock_bands.find(random_band) {|band| band > "Van Halen"} => "Britney Spears"

detect

1Note

Optional Argument for detect/find [Not Documented]

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