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Foglight 7.1.0 - Web Component Tutorial

Introducing the Web Component Framework The Web Component Framework Configuring Views and Context Queries Functions Bindings Additional Components

Required Context

If the input is marked as required, then it must be provided for the view to operate. You cannot add a component to a parent unless the parent can provide the required context. Thus, the parent view must do one of the following:

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Include that context as a required input.
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Specify that context by defining it as additional context.
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Specify that element in an instance context of one of its child components.
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Specify the element as an optional or internal input and contain another child that promises to provide a value for it.

Optional Context

If the input is marked as optional, then the view takes the data if present, otherwise it has some mechanism for inferring or calculating the data. Often this comes in the form of a drop-down list or selectable table that auto-selects the first element in the data list if a selected item is not provided. Optional Context items are those inputs that are used if they are present but are derived in some other way if they are not present. For example:

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Define a fallback value for the input. This fallback value can take the form of a query or some other mechanism. If the optional input is not available, the fallback value is taken the first time the page is loaded. Once the page has been visited, there is a persisted value. That value takes precedence over the fallback value.
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Some components such as the Drop-Down List component and Row-Oriented Table, can provide a value if one is not there. For example, if you have a drop down component with a list of Host objects you can automatically select one and post it into a Host key using the Flow Context. Adding a component such as this to a composite view then causes the optional context input value to be populated.

Internal Context

Marking a context as Internal means that the input is required for internal operation of the component and is much like the optional input, except that changes to this value by the component are not propagated to the rest of the page on an update. However, the value is propagated to the children of the component.

Internal Context items behave like optional inputs, except that when a context element changes in a nested level, the changes do not traverse up the hierarchy to the parent level. This makes it possible to have similar and dynamic views that use the same key names and types co-existing on the same page without adversely affecting each other.

You can use this type of context in a portlet with a customizer. For example, the customizer allows you to select which Host is displayed by the portlet. It is important for the component to mark the Host as internal to make sure that if two identical views are on the page at the same time, but each show data from a different host, that they do not conflict with each other.

 
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CAUTION: A view with an internal context cannot be added to a container that has the same context input, because if the view’s context changes and the page is updated, this update are not be passed on to the container. Internal Context is not for propagating context from one view to another within a page. It is designed to stop propagation of context when different parts of the page have different values for the same context.

For more information see Configuring Views .

Additional Context

Additional Context is context that is added by the view designer. The order of the additional context entries is important because the order that they are listed determines the order in which the values are evaluated (if the values are bindings).

You can add context using the Additional Context tab in the Module Contents pane to the following:

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Views
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Specific Instance of a View
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Flows
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