method

find_index

v1_8_7_330 - Show latest stable - 1 note - Class: Array

find_index(...) public

Returns the index of the first object in self such that is

to obj. If a block is given instead of an

argument, returns first object for which block is true. Returns nil if no match is found.

a = [ "a", "b", "c" ]
a.index("b")        #=> 1
a.index("z")        #=> nil
a.index{|x|x=="b"}  #=> 1

This is an alias of #find_index.

Show source

/*
 *  call-seq:
 *     array.index(obj)           ->  int or nil
 *     array.index {|item| block} ->  int or nil
 *  
 *  Returns the index of the first object in <i>self</i> such that is
 *  <code>==</code> to <i>obj</i>. If a block is given instead of an
 *  argument, returns first object for which <em>block</em> is true.
 *  Returns <code>nil</code> if no match is found.
 *     
 *     a = [ "a", "b", "c" ]
 *     a.index("b")        #=> 1
 *     a.index("z")        #=> nil
 *     a.index{|x|x=="b"}  #=> 1
 *
 *  This is an alias of <code>#find_index</code>.
 */

static VALUE
rb_ary_index(argc, argv, ary)
    int argc;
    VALUE *argv;
    VALUE ary;
{
    VALUE val;
    long i;

    if (argc  == 0) {
        RETURN_ENUMERATOR(ary, 0, 0);
        for (i=0; i<RARRAY(ary)->len; i++) {
            if (RTEST(rb_yield(RARRAY(ary)->ptr[i]))) {
                return LONG2NUM(i);
            }
        }
        return Qnil;
    }
    rb_scan_args(argc, argv, "01", &val);
    for (i=0; i<RARRAY(ary)->len; i++) {
        if (rb_equal(RARRAY(ary)->ptr[i], val))
            return LONG2NUM(i);
    }
    return Qnil;
}

July 8, 2009 - (<= v1_8_7_72)

5 thanks

Using block version in Ruby < 1.8.7

The block usage was added in 1.8.7, so to get the same functionality in an earlier version of Ruby, you need to utilize the find method.

Here is a quick example:

match = list.find { |l| l.owner == myself }
match_index = list.index(match)

If you do some gymnastics, you can have it on one line without extra variables:

match_index = list.index(list.find { |l| l.owner == myself })

find_index

Related methods

to obj. If a block is given instead of an

Using block version in Ruby < 1.8.7

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