Method: Array#one?
- Defined in:
- array.c
#one? ⇒ Boolean #one? {|element| ... } ⇒ Boolean #one?(object) ⇒ Boolean
Returns true if exactly one element of self meets a given criterion.
With no block given and no argument, returns true if self has exactly one truthy element, false otherwise:
[nil, 0].one? # => true
[0, 0].one? # => false
[nil, nil].one? # => false
[].one? # => false
With a block given, calls the block with each element in self; returns true if the block a truthy value for exactly one element, false otherwise:
[0, 1, 2].one? {|element| element > 0 } # => false
[0, 1, 2].one? {|element| element > 1 } # => true
[0, 1, 2].one? {|element| element > 2 } # => false
With argument object given, returns true if for exactly one element element, object === element; false otherwise:
[0, 1, 2].one?(0) # => true
[0, 0, 1].one?(0) # => false
[1, 1, 2].one?(0) # => false
['food', 'drink'].one?(/bar/) # => false
['food', 'drink'].one?(/foo/) # => true
[].one?(/foo/) # => false
Related: see Methods for Querying.
7975 7976 7977 7978 7979 7980 7981 7982 7983 7984 7985 7986 7987 7988 7989 7990 7991 7992 7993 7994 7995 7996 7997 7998 7999 8000 8001 8002 8003 8004 8005 8006 8007 8008 8009 8010 8011 |
# File 'array.c', line 7975
static VALUE
rb_ary_one_p(int argc, VALUE *argv, VALUE ary)
{
long i, len = RARRAY_LEN(ary);
VALUE result = Qfalse;
rb_check_arity(argc, 0, 1);
if (!len) return Qfalse;
if (argc) {
if (rb_block_given_p()) {
rb_warn("given block not used");
}
for (i = 0; i < RARRAY_LEN(ary); ++i) {
if (RTEST(rb_funcall(argv[0], idEqq, 1, RARRAY_AREF(ary, i)))) {
if (result) return Qfalse;
result = Qtrue;
}
}
}
else if (!rb_block_given_p()) {
for (i = 0; i < len; ++i) {
if (RTEST(RARRAY_AREF(ary, i))) {
if (result) return Qfalse;
result = Qtrue;
}
}
}
else {
for (i = 0; i < RARRAY_LEN(ary); ++i) {
if (RTEST(rb_yield(RARRAY_AREF(ary, i)))) {
if (result) return Qfalse;
result = Qtrue;
}
}
}
return result;
}
|