Grails nested taglibs that use templates? - grails

Question

I want to create taglibs to simplify a webpage that represents a user dashboard. There are 2 taglibs I want to create. The first is a generic panel that will be used elsewhere, the second is a more specific version of the panel.
The GSP is called from a controller with the following model:
def index() {
def timelineItems = [
[details: "Some text"],
[details: "Some other text"]
]
render(view: "index", model: [timelineItems: timelineItems])
}
My desired GSP looks like this:
<dash:panel panelClass="col-lg-8" panelTitle="Service History">
<p>Some text in the body here</p>
<dash:timelinePanel timelineItems="$timelineItems" />
</dash:panel>
I want to put my HTML code in templates to make editing it simpler, so I call render from inside the tag lib and pass a data model. The taglibs look like this (within a namespace called dash):
def panel = {attrs, body ->
out << render(template: "/dashboard/dashboardPanel", model:[panelClass: attrs.getAt("panelClass"), panelTitle: attrs.getAt("panelTitle"), body: body()])
}
def timelinePanel = { attrs ->
out << render(template: "/dashboard/dashboardTimelinePanel", model: [timelineItems: attrs.getAt("timelineItems")])
}
This is my generic panel template: it should render the data in the top divs and then simply render the body passed to it in the model:
<div class="${panelClass}">
<div class="panel panel-default">
<div class="panel-heading">
${panelTitle}
</div>
<div class="panel-body">
${body}
</div>
</div>
</div>
This is my timeline template: it should render the details of each of the timeline variables passed in the model by the controller.
<g:each in="${timelineItems}">
<p>${it.details}</p>
</g:each>
I'm expecting to see a div which includes something like:
Some text in the body here
<p>Some text</p>
<p>Some other text</p>
However, I get the following error:
Error evaluating expression [it.details] : No such property: details for class: java.lang.String
My map appears to be being converted to a string and I can't access the map. What am I doing wrong please? I want to define multiple tags which can be used inside one another. How do I do this?