Access current bindingContext in filters - is it possible to do this?

[helmut-hoffer-von-ankershoffen]

Background: we built a "trans" (translation) filter - that actually uses translation messages of a Symfony2 backend - and can be used e.g. like so:

{{ 'translate-this' | trans : 'translation-domain' }}

We want to be able to set the default translation domain like so
{{# transDefaultDomain: 'whatever' }}
{{ 'translate-this' | trans }}
{{ 'and-this' | trans }}
{{/ transDefaultDomain }}

so that for multiple translations the domain has not to be given per element ...

Therefore our trans-filter needs to access the current binding context ...

Best Regards

P.S.: We love your extension.

[mbest]

I'm hesitant to pass in the binding context or any other fixed parameters mainly because I'd like to keep the filter interface simple.

Another idea that could help is to support a per-filter preprocesor. Then you could set up something like the following:

ko.filter.trans.preprocess = function (arguments) {
    return arguments || "$context.domain";
}

For now, you can add a preprocessor function to the text binding that adds the parameter:

ko.punches.utils.addBindingPreprocessor('text', function (input) {
    return input.replace(/\| *trans/, "| trans:$context.domain");
});

(My example isn't very robust. It'll break instances of a filter that begins with "trans" or where "trans" is specified with an argument.)