[support] make a field depend on multiple fields

I want to perform an http request to get a field’s options, but only when other fields have values, other fields may get theirs options by HTTP requests

example:

fields= [
 { key: 'field1', type:'select', templateOptions:{options: http.get('/field1')},
 { key: 'field2', type:'select', templateOptions:{options: http.get('/field2')},
{
 key: 'field3',
 dependencies: ['field1', 'field2'] // <-------------------
}

[aitboudad]

Another solution is to rely on fieldChanges which emit the field options when they got resolved (https://github.com/ngx-formly/ngx-formly/issues/2350#issuecomment-658158267) but you should declare options in expressionProperties instead:

fields= [
 { key: 'field1', type:'select', expressionProperties:{'templateOptions.options': http.get('/field1')},
 ...
 {
      key: 'field3',
      hooks: {
        onInit: field => {
          field.templateOptions.options = field.options.fieldChanges....
        }
      }
 }
]

[aitboudad]

do you mean that service.get('/field3') is of type Observable or Promise instead of object?

Observable type

I see it like:

get(field:string, dependencies: string[]){
  return new Observable(sub=>{
      /* wait until all dependencies have values */
  })

yes something like that.