How to create a custom list iterator helper for handlebars in java

Question

I am using Handlebars for java from : https://github.com/jknack/handlebars.java I have a list of CustomObject and a template file template.hbs. I'm able to iterate over this list by using handle bars {{#each customList}} block.

Now I want to iterate only through even indexed objects in my customList.

Server side :

handlebars.registerHelper("even", new Helper<List<?>>() {
        @Override
        public Object apply(List<?> list, Options options)
                throws IOException {
            if(list!=null && list.size()>1) {
                for(int index=0;index<list.size();index++) {
                    if((index+1) % 2 != 0) {
                        options.fn(list.remove(index));
                    }
                }
            }
            return list;

part of Template.hbs:

{{#even customList}}
  {{customProperty1}}
{{/even}}

But this doesn't iterate my customList instead it just prints my list as string.

score 0 · Accepted Answer · answered Nov 28 '17 at 01:54

I think it's easier to use builtin pseudo vars, so you can accomplish what you ask without messing with custom helpers:

{{#customList}}
  {{#if @even}}
    {{customProperty1}}
  {{/if}}
{{/customList}}

Notice that its internal index starts at 0 (interpreted as even), if you need to invert that you can use #unless or @odd.

I also would like to point out the NumberHelper, which offers isEven, isOdd & stripes.

But if you really insist in writing your own custom helper to iterate over even-indexed elements of an Iterable, you're better off studying the source of EachHelper, there you'll also find other pseudo vars.

Thanks for giving insights on the built in pseudo vars even and odd. It serves my purpose :) — Jeba Samuel, Nov 29 '17 at 10:17

How to create a custom list iterator helper for handlebars in java

1 Answers1