Combobox constraint after binding phase

answered 2021-09-09 11:45:40 +0800

hawk
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updated 2021-09-09 13:48:18 +0800

Is there any special reason you have to set a constraint with data binding instead of EL? Since, you usually need to set it once without changing it at run-time. If so , EL works.

When you use data binding, if you don't specify a ViewModel, you have to apply BindComposer, or data binding doesn't work. I don't see it in your zkfiddle. So @load() doesn't work.

<window border="normal" title="Combobox Constraint" apply="org.zkoss.bind.BindComposer"/>

Combobox has an issue that users might enter a non-existed value, you can set it readOnly="true" to avoid this issue. Or use <searchbox> alternatively.

answered 2021-09-15 18:40:05 +0800

hawk
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updated 2021-09-17 11:56:23 +0800

why @load(cct) doesn't work in your zkfiddle

I update your case https://zkfiddle.org/sample/3l1o9r9/5-Combobox-Load-Constrain (add BindComposer), the constraint, @load(cct), is set as expected. Since in your original fiddle case, you don't use a ViewModel, you have to apply BindComposer to make data binding work.

In your real application, if the page is injected by <apply>, and you already apply its parent page with BindComposer then the data binding will work. By default, if you use a viewmodel with viewModel="@id(vm)@init(...)", zk will apply a BindComposer implicitly.

why searchbox

As I understand, the reason you put the custom constraint is to make user input can only be one of the combobox items. That's the common problem of combobox: it allows user to enter a value that doesn't exist in comboitem. You can make combobox read-only to avoid users from entering arbitrary values. Or using Searchbox.

Searchbox only allows an end-user to enter a value in its value list, so it doesn't need a custom constraint to validate user input.