Sort by nested field value in FTL liferay - freemarker

Question

My Structure created in liferay is as shown below:
{
"availableLanguageIds": [
"en_US"
],
"defaultLanguageId": "en_US",
"fields": [
{
"label": {
"en_US": "Image"
},
"predefinedValue": {
"en_US": ""
},
"style": {
"en_US": ""
},
"tip": {
"en_US": "Upload the image to be displayed in the Small Banner"
},
"dataType": "image",
"fieldNamespace": "ddm",
"indexType": "keyword",
"localizable": true,
"name": "smallImage",
"readOnly": false,
"repeatable": true,
"required": true,
"showLabel": true,
"type": "ddm-image",
"nestedFields": [
{
"label": {
"en_US": "Priority of Image"
},
"predefinedValue": {
"en_US": "0"
},
"style": {
"en_US": ""
},
"tip": {
"en_US": "Priority of the uploaded Image. Lower the number, higher the priority."
},
"dataType": "integer",
"fieldNamespace": "ddm",
"indexType": "keyword",
"localizable": true,
"name": "imagePriority",
"readOnly": false,
"repeatable": false,
"required": true,
"showLabel": true,
"type": "ddm-integer"
}
]
}
]
}
Now in the template I want to sort it using the priority field of the image. My template is as shown below:
<div id="example2" class="slider-pro">
<div class="sp-slides">
<#if smallImage.getSiblings()?has_content>
<#list smallImage.getSiblings()?sort_by(["properties","imagePriority"]) as cur_smallImage>
<#if cur_smallImage.getData()?? && cur_smallImage.getData() != "">
<div class="sp-slide">
<img class="sp-image" alt="${cur_smallImage.getAttribute("alt")}" src="${cur_smallImage.getData()}" data-src="${cur_smallImage.getData()}" data-retina="${cur_smallImage.getData()}" />
</div>
</#if>
</#list>
</#if>
</div>
</div>
I tried the sorting as ?sort_by("cur_smallImage.imagePriority") also by ?sort_by("imagePriority") but it didnt work. I want to display the images in the sequence of the priority specified.
Please help.

Answer 1

If the subvariable that you want to use for the sorting is on a deeper level (that is, if it is a subvariable of a subvariable and so on), then you can use a sequence as parameter, that specifies the names of the sub variables that lead down to the desired subvariable. For example:
<#assign members = [
{"name": {"first": "Joe", "last": "Smith"}, "age": 40},
{"name": {"first": "Fred", "last": "Crooger"}, "age": 35},
{"name": {"first": "Amanda", "last": "Fox"}, "age": 25}]>
Sorted by name.last:
<#list members?sort_by(['name', 'last']) as m>
- ${m.name.last}, ${m.name.first}: ${m.age} years old
</#list>
taken from:
https://freemarker.apache.org/docs/ref_builtins_sequence.html#ref_builtin_sort_by