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instance method
Array#fetch
(::int index) -> Elem
[T] (::int index, T default) -> (Elem | T)
[I < ::_ToInt, T] (I index) { (I index) -> T } -> (Elem | T)
fetch(index) → element
fetch(index, default_value) → element or default_value
fetch(index) {|index| ... } → element or block_return_value
array.c
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static VALUE
rb_ary_fetch(int argc, VALUE *argv, VALUE ary)
{
VALUE pos, ifnone;
long block_given;
rb_len_t idx;
rb_scan_args(argc, argv, "11", &pos, &ifnone);
block_given = rb_block_given_p();
if (block_given && argc == 2) {
rb_warn("block supersedes default value argument");
}
idx = NUM2LEN(pos);
if (idx < 0) {
idx += RARRAY_LEN(ary);
}
if (idx < 0 || RARRAY_LEN(ary) <= idx) {
if (block_given) return rb_yield(pos);
if (argc == 1) {
rb_raise(rb_eIndexError, "index %"PRIdLEN" outside of array bounds: %"PRIdLEN"...%"PRIdLEN,
idx - (idx < 0 ? RARRAY_LEN(ary) : 0), -RARRAY_LEN(ary), RARRAY_LEN(ary));
}
return ifnone;
}
return RARRAY_AREF(ary, idx);
}
Returns the element of self at offset index if index is in range; index must be an integer-convertible object.
With the single argument index and no block, returns the element at offset index:
Example
a = [:foo, 'bar', 2] a.fetch(1) # => "bar" a.fetch(1.1) # => "bar"
If index is negative, counts from the end of the array:
Example
a = [:foo, 'bar', 2] a.fetch(-1) # => 2 a.fetch(-2) # => "bar"
With arguments index and default_value (which may be any object) and no block, returns default_value if index is out-of-range:
Example
a = [:foo, 'bar', 2] a.fetch(1, nil) # => "bar" a.fetch(3, :foo) # => :foo
With argument index and a block, returns the element at offset index if index is in range (and the block is not called); otherwise calls the block with index and returns its return value:
Example
a = [:foo, 'bar', 2] a.fetch(1) {|index| raise 'Cannot happen' } # => "bar" a.fetch(50) {|index| "Value for #{index}" } # => "Value for 50"
Related: see Methods for Fetching.