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instance method
Hash#shift
hash.shift → [key, value] or default_value
hash.c
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static VALUE
rb_hash_shift(VALUE hash)
{
struct shift_var var;
rb_hash_modify_check(hash);
if (RHASH_AR_TABLE_P(hash)) {
var.key = Qundef;
if (RHASH_ITER_LEV(hash) == 0) {
if (ar_shift(hash, &var.key, &var.val)) {
return rb_assoc_new(var.key, var.val);
}
}
else {
rb_hash_foreach(hash, shift_i_safe, (VALUE)&var);
if (var.key != Qundef) {
rb_hash_delete_entry(hash, var.key);
return rb_assoc_new(var.key, var.val);
}
}
}
if (RHASH_ST_TABLE_P(hash)) {
var.key = Qundef;
if (RHASH_ITER_LEV(hash) == 0) {
if (st_shift(RHASH_ST_TABLE(hash), &var.key, &var.val)) {
return rb_assoc_new(var.key, var.val);
}
}
else {
rb_hash_foreach(hash, shift_i_safe, (VALUE)&var);
if (var.key != Qundef) {
rb_hash_delete_entry(hash, var.key);
return rb_assoc_new(var.key, var.val);
}
}
}
return rb_hash_default_value(hash, Qnil);
}
Removes the first hash entry (see Entry Order); returns a 2-element Array containing the removed key and value:
Example
h = {foo: 0, bar: 1, baz: 2} h.shift # => [:foo, 0] h # => {:bar=>1, :baz=>2}
Returns the default value if the hash is empty (see Default Values).