THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
...
| Code Block | ||
|---|---|---|
| ||
<html xmlns:t="http://tapestry.apache.org/schema/tapestry_5_34.xsd"> <t:pagelink page="Index">Go Home</t:pagelink> </html> |
...
The component above can be referenced in another component or page template, and its parameters bound:
| Code Block | ||
|---|---|---|
| ||
<html t:type="layout" xmlns:t="http://tapestry.apache.org/schema/tapestry_5_34.xsd"> <p> Merry Christmas: <t:count end="3"> Ho! </t:count> </p> </html> |
The end attribute is used to bind the end parameter of the Count component. Here, it is being bound to the string value "3", which is automatically coerced by Tapestry into the int value, 3.
...
Prefix | Description |
|---|---|
asset: | The relative path to an asset file (which must exist) |
block: | The id of a block within the template |
component: | The id of another component within the same template |
context: | Context asset: path from context root |
literal: | A literal string |
nullfieldstrategy: | Used to locate a pre-defined NullFieldStrategy |
message: | Retrieves a string from the component's message catalog |
prop: | A property expression to read or update |
symbol: | Used to read one of your symbols |
translate: | The name of a configured translator |
validate: | A validator specification used to create some number of field validators |
var: | Allows a render variable of the component to be read or updated |
...
| Tip |
|---|
Sometimes a parameter is marked as required, but may still be omitted if the underlying value is provided by some other means. This is the case, for example, with the Select component's value parameter, which may have its underlying value set by contributing a ValueEncoderSource. Be sure to read the component's parameter documentation carefully. Required simply enables checks that the parameter is bound, it does not mean that you must supply the binding in the template (or @Component annotation). |
...
Don't use the ${...} syntax!
Main Article: Expansions
You generally should not use the Template Expansion syntax, ${...}, within component parameter bindings. Doing so results in the property inside the braces being converted to an (immutable) string, and will therefore result in a runtime exception if your component needs to update the value (whenever the default or explicit binding prefix is prop: or var:, since such component parameters are two-way bindings).
...
| Code Block | ||
|---|---|---|
| ||
<t:layout xmlns:t="http://tapestry.apache.org/schema/tapestry_5_34.xsd"> <p> Countdown: <t:count start="5" end="1" result="index"> ${index} ... </t:count> </p> </t:layout> |
...
| Code Block | ||||
|---|---|---|---|---|
| ||||
<html xmlns:t="http://tapestry.apache.org/schema/tapestry_5_34.xsd"> <body> <div t:type="layout" t:menuTitle="literal:The Title"> ... </div> </body> </html> |
| Code Block | ||||
|---|---|---|---|---|
| ||||
<t:container xmlns:t="http://tapestry.apache.org/schema/tapestry_5_34.xsd"> <div t:type="title" t:title="inherit:menuTitle"></div> <t:body /> </t:container> |
...
Tapestry includes a mechanism for coercing types automatically. Most often, this is used to convert literal strings into appropriate values, but in many cases, more complex conversions will occur. This mechanism is used for component parameters, such as when an outer component passes a literal string to an inner component that is expecting an integer.
You can easily contribute new coercions for your own purposes.
Parameter Names
...
In rare cases, you may want to take different behaviors based on whether a parameter is bound or not. This can be accomplished by querying the component's resources, which can be injected into the component using the @Inject annotation:
| Code Block | ||
|---|---|---|
| ||
public class MyComponent
{
@Parameter
private int myParam;
@Inject
private ComponentResources resourcescomponentResources;
@BeginRender
void setup()
{
if (resourcescomponentResources.isBound("myParam"))
{
. . .
}
}
}
|
...
| Code Block | ||||
|---|---|---|---|---|
| ||||
<t:container xmlns:t="http://tapestry.apache.org/schema/tapestry_5_34.xsd"> <t:pageLink t:id="link">Page Link</t:pageLink> </t:container> |
...