Kefir model

kefir.model.js

/////////////
// Factory //
/////////////
 
Kefir.model = function (store, tx) {
   if (typeof tx !== 'function') tx = x => x;
 
   const getset = function kefir$model (update) {
      if (arguments.length > 0) {
         let value = tx(update, (getset._currentEvent || {}).value);
 
         if (getset._alive) {
            // Active property (kefir will update current value)
            getset._emitValue(value);
         } else {
            // In-active property (manually set current value)
            getset._currentEvent = { type: VALUE, value: value };
         }
 
         return value;
      }
      return (getset._currentEvent || {}).value;
   };
 
   // Copy property methods to model
   let proto = Kefir.Property.prototype;
   for (var x in proto) getset[x] = proto[x];
   Kefir.Property.call(getset);
 
   getset._currentEvent = { type: VALUE, value: store };
 
   return getset;
};
 
///////////////
// Converter //
///////////////
 
Kefir.Observable.prototype.toModel = function(store, tx) {
   if (typeof tx !== 'function') tx = x => x;
 
   // Sources
   let model = Kefir.model(store, tx);
   let obs = this.map(update => tx(update, store));
 
   let getset = function (update) {
      if (arguments.length > 0) {
         store = model(update);
      }
      return store;
   };
 
   // Output
   const combined = Kefir
      .merge([model.skip(1), obs])
      .map(val => (store = val))   // Assignment
      .toProperty(() => store);

   for (let x in combined) getset[x] = combined[x];
 
   return getset;
};

Usage

Both methods expect the following arguments. The transformer function if provided receives (inputValue, currentModelState) as arguments and is expected to return the update model state.

Arguments

1. seed (Any): The initial value of the model
2. [transformer=identity] (Function): Transformer invoked for all incoming values; either from setter interface or (in case of obs.toModel(), additionally from the base observable)

Returns

(Function): Getter/setter function. Call without an argument to get latest model state. Call with a single argument to set new model state.