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39 lines
1.8 KiB
Plaintext
39 lines
1.8 KiB
Plaintext
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ABOUT THE CODE
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WHAT HAPPENS WHEN A TEMPLATE EDITOR IS OPENED FOR A RESOURCE
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The template editor uses a dedicated class for each field type (or family of field types).
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These classes are all subclasses of the common base class NuTemplateElement. For things like
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lists, there is a subclass NuTemplateGroupElement from which you can instead subclass to
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have some of the work done for you.
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When opening a resource, the template editor first creates a NuTemplateStream for the template
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resource and calls readOneObject: on it until it runs out of data, instantiating a hierarchy
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of NuTemplateElement subclasses for based on the template.
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After that, it creates a NuTemplateStream for the resource and loops over the template object
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hierarchy, creating a copy of each item, and then calling readDataFrom:containingArray: on
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the copy, which in turn reads data from the NuTemplateStream and stores it in its instance
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variables. For this to work, subclasses of NuTemplateElement *must* implement the NSCopying
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protocol.
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This results in an object hierarchy that describes the entire resource using template fields
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containing the data, which can now be edited, displayed in lists, etc.
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WHAT HAPPENS WHEN THE TEMPLATE EDITOR IS CLOSED
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As soon as the template editor is closed, another NuTemplateStream is created for the
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resource and passed to all template fields (the copies with the resource data, not the
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pre-parsed template hierarchy), via writeDataTo:, which is where they should write their
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data to the stream. Before that, sizeOnDisk is called on each NuTemplateElement to
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calculate the new size of the resource before the actual process of writing them out.
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This size must include the size of all of their sub-items, and writeDataTo: must call
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these sub items if they are to be written to disk.
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SPECIAL CASE: LISTS
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