groowt/web-views/docs/asciidoc/componentTemplateSpec.asciidoc

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= Component Template Specification
== Compiled Component Template Code
The following code represents a typical (transpiled) component template:
[source, groovy]
----
package com.jessebrault.website
import groowt.view.component.ComponentTemplate
import groowt.view.component.context.ComponentContext
import groowt.view.component.runtime.*
import groowt.view.web.WebViewComponent
import groowt.view.web.lib.*
import groowt.view.web.runtime.*
class MyComponentTemplate implements ComponentTemplate {
Closure getRenderer() {
return { ComponentContext componentContext, ComponentWriter out ->
// <1>
final RenderContext renderContext = new DefaultWebViewComponentRenderContext(componentContext, out)
componentContext.setRenderContext(renderContext)
out.setRenderContext(renderContext)
out.setComponentContext(renderContext)
out.append 'Hello from simple text!' // <2>
out.append "Hello from GString!" // <3>
// <4>
ComponentContext.Resolved c0Resolved // <5>
try {
c0Resolved = renderContext.resolve('MySubComponent', MySubComponent) // <6>
} catch (ComponentResolveException c0ResolveException) { // <7>
c0ResolveException.template = this
c0ResolveException.line = 1
c0ResolveException.column = 1
throw c0ResolveException
}
WebViewComponent c0 // <8>
try {
c0 = renderContext.create( // <9>
c0Resolved,
[greeting: 'Hello, World!'],
"Some constructor arg",
WebViewComponentChildCollectorClosure.get(this) { c0cc ->
c0cc.add 'JString child.' // <10>
c0cc.add "GString child"
ComponentContext.Resolved c1Resolved
try {
c1Resolved = renderContext.resolve('h1') // <11>
} catch (ComponentResolveException c1ResolveException) {
c1ResolveException.type = IntrinsicHtml // <12>
c1ResolveException.template = this
c1ResolveException.line = 1
c1ResolveException.column = 10
throw c1ResolveException
}
WebViewComponent c1
try {
c1 = renderContext.create(
c1_resolved,
WebViewComponentChildCollectorClosure.get(this) { c1cc ->
c1cc.add "$greeting"
}
)
} catch (ComponentCreateException c1CreateException) {
c1CreateException.template = this
c1CreateException.line = 1
c1CreateException.column = 1
}
c0cc.add c1
}
)
} catch (ComponentCreateException c0CreateException) {
c0CreateException.template = this
c0CreateException.line = 1
c0CreateException.column = 1
throw c0CreateException
}
// append it
out.append c0
}
}
}
----
<1> Initialize the contexts.
<2> Appending a plain old java string (jstring) to `out`.
<3> Appending a GString to `out`.
<4> Now begins a component 'block', where a component is resolved, created, and either rendered or appended
to a child collector (see below).
<5> First, we define the `resolved` variable, of the type `ComponentContext.Resolved`.
<6> Resolve it from the context.
<7> If the context cannot resolve the component, it should throw a `ComponentResolveException`. We catch it
here in order to set the template (`this`), line, and column information for debugging purposes.
<8> Now we can start to create the component by first defining a variable for it.
<9> The create function takes a few things:
. The relevant instance of `ComponentContext.Resolved`.
. Any attributes for the component, passed as a `Map`.
. Any arguments from the component constructor.
. A `WebViewComponentChildCollectorClosure`, which is a 'marker' subclass of `Closure`
(so that constructor args ending with a closure don't get confused), which simply collects
the children of the component.
<10> For children, we add the value of the child, rather than appending it directly to `out`.
The collector itself will be given the `out` writer from the `context`, which will then
supply the parent with the ability to render to out. This way the parent doesn't ever have to worry about `out` itself
(though if the parent wants access to `out` (for example, it is using a non-wvc template) it can access the out writer
from the context).
<11> Here, a string type is passed, since all lowercase type names are treated as string types in web view components.
<12> Because this is an intrinsic html element, we set the type here.
<13> Finally, our child component is added as a `Closure` which accepts the component back again and appends
it to out.
== Items requiring Groovy ASTNode position adjustment
The following items all need to have their transpiled Groovy ASTNodes' positions adjusted to match the original source
file, in case there is a Groovy compilation error involved.
* JStrings
* GStrings
* Component types (Class and String expressions)
* Attribute keys and values
* Component constructor args