Deferred Data Access

Deferred Data Access(DDA) is a framework for building async CRUD APIs. It transforms object calls into commands that can be interpreted by custom function.

How it works

1. Framework accepts an async handler function and returns an object.

const obj = handle((command, context) => {
  let result;

  // Some logic that gets somewhere value and saves in into "result" variable.

  return result;
})();

2. Developer accesses object property and gets Promise

const value = await obj.prop;

3. Framework records property access into a command object, handler function is called with command object as an argument.

{ type: ProxyCommand.GET, name: 'prop' }

4. Whatever function returns is returned as promise value.

DDA can operate in two modes, mode is defined by passing second argument to handle() function.

• lazy - Default mode, custom handler function is called only when then() or catch() methods are accessed. Accessing obj.child.grand.prop.then(func) calls function once.
• reactive - Non-lazy, custom handler function called on every operation. Accessing obj.child.grand.prop.then(func) calls function 3 times.

There are multiple predefined commands that can be passed to handler function.

• ProxyCommand.GET - when property accessed
• ProxyCommand.SET - when property is set, new value is recorded as value in command object
• ProxyCommand.DELETE_PROPERTY - when property is being deleted
• ProxyCommand.APPLY - when function is called, call arguments recorded as value of command object
• ProxyCommand.METHOD_CALL - only generated in lazy mode, it combines GET and APPLY commands.

Projects made with DDA

• RESTObject
• WorkerInterface