Proc#parameters

prc.parameters(lambda: nil) → array

static VALUE
rb_proc_parameters(int argc, VALUE *argv, VALUE self)
{
    static ID keyword_ids[1];
    VALUE opt, lambda;
    VALUE kwargs[1];
    int is_proc ;
    const rb_iseq_t *iseq;

    iseq = rb_proc_get_iseq(self, &is_proc);

    if (!keyword_ids[0]) {
        CONST_ID(keyword_ids[0], "lambda");
    }

    rb_scan_args(argc, argv, "0:", &opt);
    if (!NIL_P(opt)) {
        rb_get_kwargs(opt, keyword_ids, 0, 1, kwargs);
        lambda = kwargs[0];
        if (!NIL_P(lambda)) {
            is_proc = !RTEST(lambda);
        }
    }

    if (!iseq) {
        return rb_unnamed_parameters(rb_proc_arity(self));
    }
    return rb_iseq_parameters(iseq, is_proc);
}

Returns the parameter information of this proc. If the lambda keyword is provided and not nil, treats the proc as a lambda if true and as a non-lambda if false.

Example

prc = proc{|x, y=42, *other|}
prc.parameters  #=> [[:opt, :x], [:opt, :y], [:rest, :other]]
prc = lambda{|x, y=42, *other|}
prc.parameters  #=> [[:req, :x], [:opt, :y], [:rest, :other]]
prc = proc{|x, y=42, *other|}
prc.parameters(lambda: true)  #=> [[:req, :x], [:opt, :y], [:rest, :other]]
prc = lambda{|x, y=42, *other|}
prc.parameters(lambda: false) #=> [[:opt, :x], [:opt, :y], [:rest, :other]]

Ruby version changes

3.2
- Proc#parameters now accepts lambda keyword. [Feature #15357]

See also #lambda? #ruby2_keywords #inspect #source_location also in 4.1 · 4.0 · 3.4 · 3.2 · 3.1 · 3.0

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