Apple WebObjects 3.5 Bedienungsanleitung PDF herunterladen (Seite 106)

Chapter 6 Creating Reusable Components

106

that were linked in to the application executable for a component with that

name. For example, applications written entirely in WebScript use the default

application executable,

WODefaultApp. This executable is linked to the frameworks

WebObjects.framework and WOExtensions.framework, so any components deﬁned in either

of these two frameworks can be used in a scripted application.

Designing for Reusability

Here are some points to consider when creating reusable components:

• Make sure that your reusable component generates HTML that can be

embedded in the HTML of its parent component.

A reusable component should be designed to be a “good citizen” within

the context in which it will be used. Thus, for example, the template ﬁle

for a reusable component should not start and end with the <HTML> and

</HTML> tags (since these tags will be supplied by the parent

component). Similarly, it is unlikely that a reusable component’s template

would contain <BODY>, <HEAD>, or <TITLE> tags.

Further, if you intend your component to be used within a form along with

other components, don’t declare the form (<FORM...> ... </FORM>)

within the reusable component’s template ﬁle. Instead, let the parent

component declare the form. Similar considerations pertain to submit

buttons. Since most browsers allow only one submit button within a form,

putting a submit button in a reusable component severely limits where it

can be used.

• Guard against name conﬂicts.

Reusable components are identiﬁed by name only. See “Search Path for

Reusable Components” (page 105). Those that reside within a particular

application’s application directory are available only to that application.

Those that reside in a framework (for example,

WOExtensions.framework) are

available to all applications that link to it. Suppose you have a component

named NavigationControl in your application and one of the frameworks

that your application links to also has a NavigationControl component.

Which one will be used in your application? The result is unpredictable.

Reusable component names need to be systemwide unique. Consider

adding a preﬁx to component names to increase the likelihood that they

will be unique.

1 2 ... 101 102 103 104 105 106 107 108 109 110 111 ... 217 218

Keine Kommentare

Apple WebObjects 3.5 Bedienungsanleitung Seite 106