Render Template Collaboration

In this collaboration, we use a compiled TAL to render text.

Objects

PT – The PageTemplate

PT2 – Another PageTemplate

TI – An object that implements the TALImplementation interface.

CTAL – A compiled TAL data structure returned from a TAL compile

call.

CTAL2 – ditto.

EEF – An object that implements the ExpressionEngineFactory interface.

EE – An object that implements the ExpressionEngine interface.

cexpr – A compiled expression. This will be context-dependent. For

example, when we are executing a define. this will be a different expression for each definition.

Sequence of calls

• PT calls EEF.create(data)

  to create an expression engine. The expression is passed names to be included in the standard namespace. The call returns an expression engine, EE.

• PT calls TI.renderText(CTAL, EE)

  As the TALImplementation renders the TAL, it will make calls to EE as different TAL statements are executed:

  When a node containing a define or a repeat is encountered (and a condition, if present, if true):

  • TI calls EE.beginScope()

  After processing node containing a define or a loop:

  • TI calls EE.endScope()

  when a z:define is executed:

  For each define (in order), either:

  • TI calls EE.setLocal(name, cexpr)

  or

  • TI calls EE.setGlobal(name, cexpr)

  For each condition:

  • TI calls EE.isTrue(cexpr)

  For each repeat:

  • TI calls EE.startRepeat(name, cexpr)

  while 1:

  • TI calls EE.repeat()

    The return value is a boolean. If the value is false, we break out of the loop. Otherwise, we render the output node and continue.

  For each insert or replace:

  • TI calls EE.text(cexpr)

    To compute the text to be used. The return value is either a string, None, or an object that satisfies the DOM text-node interface.

  or

  • TI calls EE.structure(cexpr)

    To compute the structure to be inserted. The result should be a DOM Fragment or None.

  For each attribute to be set:

  • TI calls EE.text(cexpr)

    to compute the attribute text. The result should be a string or None.

  When a use-macro is encountered,

  • TI calls EE.macro(cexpr)

    The expression engine evaluates the expression. This is likely to involve traversal into a PageTemplate, which will ask the TAL implementation for the macro.

    PT2 calls TI.findMacro(CTAL2, name)