Apple Newton Utilities Betriebsanweisung PDF herunterladen (Seite 109)

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CHAPTER 3

Views

About Views 3-25

_parent Contains a reference to the parent template. This slot is

created when the view opens. Note that it’s best to use the

Parent function to access the parent view at run time, rather

than directly referencing the

_parent slot.

stepChildren Contains an array that holds references to each of the

template’s child templates. This slot is created and set

automatically when you graphically create child views in

NTK. This slot is for children that you add to a template.

viewChildren Contains an array that holds references to each of a system

proto’s child templates. Because this slot is used by system

protos, you should never modify it or create a new one with

this name. If you do so, you may be inadvertently overriding

the children of a system proto. An exception to this rule

occurs for clEditView; you might want to edit the

viewChildren slot of a clEditView. See Table 2-1, “View

class constants,” (page 2-2) in Newton Programmer’s Guide

for details.

The reason for the dual child view slots is that the

viewChildren slot is used by

the system protos to store their child templates. If you create a view derived from

one of the system protos and change the

viewChildren slot (for example, to add

your own child templates programmatically), you would actually be creating a new

viewChildren slot that would override the one in the proto, and the child

templates of the proto would be ignored.

The

stepChildren slot has been provided instead as a place for you to put your

child templates, if you need to do so from within a method. By adding your

templates to this slot, the

viewChildren slot of the proto is not overridden. Both

groups of child views are created when the parent view is instantiated.

If you are only creating views graphically using the Newton Toolkit palette, you don’t

need to worry about these internal details. The Newton Toolkit always uses the

stepChildren slot for you.

You may see either

viewChildren, stepChildren, or both slots when you

examine a template at run time in the Newton Toolkit Inspector window. Child

templates can be listed in either slot, or both. When a view is instantiated, all the

child views from both of these two slots are also created. Note that the templates in

the

viewChildren slot are instantiated ﬁrst, followed by the templates in the

stepChildren slot.

If you are adding child views in a method that will not be executed until run time,

you need to use the

stepChildren slot to do this. If there isn’t a

stepChildren slot, create one and put your views there.

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