Mercurial > genshi > mirror
comparison markup/template.py @ 44:436e30c8420b trunk
implement `py:choose/when/otherwise` directives for conditionally selecting one of several blocks
| author | mgood |
|---|---|
| date | Mon, 03 Jul 2006 23:55:03 +0000 |
| parents | ee669cb9cccc |
| children | a5d585dd38c4 |
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| 43:e03b77726756 | 44:436e30c8420b |
|---|---|
| 501 else: | 501 else: |
| 502 for event in stream: | 502 for event in stream: |
| 503 yield event | 503 yield event |
| 504 | 504 |
| 505 | 505 |
| 506 class ChooseDirective(Directive): | |
| 507 """Implementation of the `py:choose` directive for conditionally selecting | |
| 508 one of several body elements to display. | |
| 509 | |
| 510 If the `py:choose` expression is empty the expressions of nested `py:when` | |
| 511 directives are tested for truth. The first true `py:when` body is output. | |
| 512 | |
| 513 >>> ctxt = Context() | |
| 514 >>> tmpl = Template('''<div xmlns:py="http://purl.org/kid/ns#" | |
| 515 ... py:choose=""> | |
| 516 ... <span py:when="0 == 1">0</span> | |
| 517 ... <span py:when="1 == 1">1</span> | |
| 518 ... </div>''') | |
| 519 >>> print tmpl.generate(ctxt) | |
| 520 <div> | |
| 521 <span>1</span> | |
| 522 </div> | |
| 523 | |
| 524 If multiple `py:when` bodies match only the first is output. | |
| 525 >>> tmpl = Template('''<div xmlns:py="http://purl.org/kid/ns#" | |
| 526 ... py:choose=""> | |
| 527 ... <span py:when="1 == 1">1</span> | |
| 528 ... <span py:when="2 == 2">2</span> | |
| 529 ... </div>''') | |
| 530 >>> print tmpl.generate(ctxt) | |
| 531 <div> | |
| 532 <span>1</span> | |
| 533 </div> | |
| 534 | |
| 535 If the `py:choose` directive contains an expression, the nested `py:when` | |
| 536 directives are tested for equality to the `py:choose` expression. | |
| 537 >>> tmpl = Template('''<div xmlns:py="http://purl.org/kid/ns#" | |
| 538 ... py:choose="2"> | |
| 539 ... <span py:when="1">1</span> | |
| 540 ... <span py:when="2">2</span> | |
| 541 ... </div>''') | |
| 542 >>> print tmpl.generate(ctxt) | |
| 543 <div> | |
| 544 <span>2</span> | |
| 545 </div> | |
| 546 | |
| 547 If no `py:when` directive is matched then the fallback directive | |
| 548 `py:otherwise` will be used. | |
| 549 >>> tmpl = Template('''<div xmlns:py="http://purl.org/kid/ns#" | |
| 550 ... py:choose=""> | |
| 551 ... <span py:when="False">hidden</span> | |
| 552 ... <span py:otherwise="">hello</span> | |
| 553 ... </div>''') | |
| 554 >>> print tmpl.generate(ctxt) | |
| 555 <div> | |
| 556 <span>hello</span> | |
| 557 </div> | |
| 558 | |
| 559 `py:choose` blocks can be nested: | |
| 560 >>> tmpl = Template('''<div xmlns:py="http://purl.org/kid/ns#" | |
| 561 ... py:choose="1"> | |
| 562 ... <div py:when="1" py:choose="3"> | |
| 563 ... <span py:when="2">2</span> | |
| 564 ... <span py:when="3">3</span> | |
| 565 ... </div> | |
| 566 ... </div>''') | |
| 567 >>> print tmpl.generate(ctxt) | |
| 568 <div> | |
| 569 <div> | |
| 570 <span>3</span> | |
| 571 </div> | |
| 572 </div> | |
| 573 | |
| 574 Behavior is undefined if a `py:choose` block contains content outside a | |
| 575 `py:when` or `py:otherwise` block. Behavior is also undefined if a | |
| 576 `py:otherwise` occurs before `py:when` blocks. | |
| 577 """ | |
| 578 | |
| 579 def __call__(self, stream, ctxt): | |
| 580 if self.expr: | |
| 581 self.value = self.expr.evaluate(ctxt) | |
| 582 self.matched = False | |
| 583 ctxt.push(__choose=self) | |
| 584 for event in stream: | |
| 585 yield event | |
| 586 ctxt.pop() | |
| 587 | |
| 588 | |
| 589 class WhenDirective(Directive): | |
| 590 """Implementation of the `py:when` directive for nesting in a parent with | |
| 591 the `py:choose` directive. See the documentation of `py:choose` for | |
| 592 usage. | |
| 593 """ | |
| 594 def __call__(self, stream, ctxt): | |
| 595 choose = ctxt['__choose'] | |
| 596 if choose.matched: | |
| 597 return [] | |
| 598 value = self.expr.evaluate(ctxt) | |
| 599 try: | |
| 600 if value == choose.value: | |
| 601 choose.matched = True | |
| 602 return stream | |
| 603 except AttributeError: | |
| 604 if value: | |
| 605 choose.matched = True | |
| 606 return stream | |
| 607 return [] | |
| 608 | |
| 609 | |
| 610 class OtherwiseDirective(Directive): | |
| 611 """Implementation of the `py:otherwise` directive for nesting in a parent | |
| 612 with the `py:choose` directive. See the documentation of `py:choose` for | |
| 613 usage. | |
| 614 """ | |
| 615 def __call__(self, stream, ctxt): | |
| 616 choose = ctxt['__choose'] | |
| 617 if choose.matched: | |
| 618 return [] | |
| 619 choose.matched = True | |
| 620 return stream | |
| 621 | |
| 622 | |
| 506 class Template(object): | 623 class Template(object): |
| 507 """Can parse a template and transform it into the corresponding output | 624 """Can parse a template and transform it into the corresponding output |
| 508 based on context data. | 625 based on context data. |
| 509 """ | 626 """ |
| 510 NAMESPACE = Namespace('http://purl.org/kid/ns#') | 627 NAMESPACE = Namespace('http://purl.org/kid/ns#') |
| 517 ('for', ForDirective), | 634 ('for', ForDirective), |
| 518 ('if', IfDirective), | 635 ('if', IfDirective), |
| 519 ('replace', ReplaceDirective), | 636 ('replace', ReplaceDirective), |
| 520 ('content', ContentDirective), | 637 ('content', ContentDirective), |
| 521 ('attrs', AttrsDirective), | 638 ('attrs', AttrsDirective), |
| 522 ('strip', StripDirective)] | 639 ('strip', StripDirective), |
| 640 ('choose', ChooseDirective), | |
| 641 ('when', WhenDirective), | |
| 642 ('otherwise', OtherwiseDirective)] | |
| 523 _dir_by_name = dict(directives) | 643 _dir_by_name = dict(directives) |
| 524 _dir_order = [directive[1] for directive in directives] | 644 _dir_order = [directive[1] for directive in directives] |
| 525 | 645 |
| 526 def __init__(self, source, basedir=None, filename=None): | 646 def __init__(self, source, basedir=None, filename=None): |
| 527 """Initialize a template from either a string or a file-like object.""" | 647 """Initialize a template from either a string or a file-like object.""" |