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.\" ========================================================================
.\"
.IX Title "UR::Iterator 3pm"
.TH UR::Iterator 3pm "2019-01-02" "perl v5.28.1" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
UR::Iterator \- API for iterating through data
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 4
\&  my $iter = UR::Iterator\->create_for_list(1, 2, 3, 4);
\&  while (my $i = $iter\->next) {
\&    print $i\en";
\&  }
\&
\&  my $mapped_iter = $iter\->map(sub { $_ + 1 });
\&  while (my $i = $mapped_iter\->next) {
\&    print "$i\en";
\&  }
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
UR::Iterator instances implement the iterator pattern.  These objects can
be created with either a list of values, or by applying a mapping function
to another iterator.
.PP
UR::Iterator instances are normal Perl object references, not UR-based
objects.  They do not live in the Context's object cache, and obey the
normal Perl rules about scoping.
.SH "METHODS"
.IX Header "METHODS"
.IP "create_for_list" 4
.IX Item "create_for_list"
.Vb 1
\&  $iter = UR::Object::Iterator\->create_for_list(@values);
.Ve
.Sp
Creates an iterator based on values contained in the given list.  This
constructor will throw an exception if any of the supplied values is
\&\f(CW\*(C`undef\*(C'\fR.
.IP "map" 4
.IX Item "map"
.Vb 1
\&  $new_iter = $iter\->map(sub { $_ + 1 });
.Ve
.Sp
Creates a new iterator based on an existing iterator.  Values returned by this
new iterator are based on the values of the existing iterator after going
through a mapping function.  This new iterator will  be exhausted when the
original iterator is exhausted.
.Sp
When the mapping function is called, \f(CW$_\fR is set to the value obtained from
the original iterator.
.IP "next" 4
.IX Item "next"
.Vb 1
\&  $obj = $iter\->next();
.Ve
.Sp
Return the next object matching the iterator's rule.  When there are no more
matching objects, it returns undef.
.IP "peek" 4
.IX Item "peek"
.Vb 1
\&  $obj = $iter\->peek();
.Ve
.Sp
Return the next object matching the iterator's rule without removing it.  The
next call to \fBpeek()\fR or \fBnext()\fR will return the same object.  Returns undef if
there are no more matching objects.
.Sp
This is useful to test whether a newly created iterator matched anything.
.IP "remaining" 4
.IX Item "remaining"
.Vb 1
\&  @objs = $iter\->remaining();
.Ve
.Sp
Return a list of all the objects remaining in the iterator.  The list will be
empty if there is no more data.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
UR::Object::Iterator