jameslaneconkling / falcor-local-datasource Goto Github PK

to log the returned JSONGraphEnvelope from get/set/call. This could help understand the relationship between:

• a request's pathSets
• the dataSource's JSONGraphEnvelope response
• the model's JSONEnvelope response

Sometimes I wonder if anyone tests out their posted code. In your example, under the todos key, you use ids 'id_0' and 'id_1', while under the key todosById you use ids 'id_1' and 'id_2'.

Version 1.2.0 (the latest, as far as I know) - in utils.js function isPathValues() fails to check if it has been passed an array. So, if you pass it a JSONGraphEnvelope, which is an object, an exception is thrown when the function calls .reduce() on it. A simple "Array.isArray(pathValues) &&" preceding that fixes the problem.

The sample code seems to work fine, but the problem is that if you ask for the number of todos before AND between the 2 calls, you'll get 2. However, if you ask for the number of todos AFTER the 2 calls, you'll get 4! Here is my code. Note that I used the code in the README file to set up the model, but used (my preferred) async/await to query the model. I did need to make these changes:

1. Create and call a function main() so I could mark it as an async function, and therefore use await.
2. Use require('falcor-local-datasource') to retrieve the LocalDatasource object
3. Fixed an issue with the id's used, which I previously reported and thought was fixed, but it looks like it's still there (i.e. using 'id_0' and 'id_1' in one place, but 'id_1' and 'id_2' in another place)

const falcor = require('falcor');
// const LocalDatasource = require('../src/index');
const LocalDatasource = require('falcor-local-datasource');

async function main() {

const graph = {
  todos: {
    0: { $type: 'ref', value: ['todosById', 'id_0'] },
    1: { $type: 'ref', value: ['todosById', 'id_1'] },
    length: 2,
    add(graph, args) {
      const newTodoLabel = args[0];
      const todoCount = graph.todos.length;
      // NOTE: this is a pretty naive way to derive new ids.  a more robust approach might generate unique ids using
      // a specific node in the graph, or use a closure, or some other mechanism to yield unique incremental values
      const newId = `id_${todoCount}`;

      // return array of pathValues
      return [
        {
          path: ['todos', todoCount],
          value: { $type: 'ref', value: ['todosById', newId] }
        },
        {
          path: ['todosById', newId, 'label'],
          value: newTodoLabel
        },
        {
          path: ['todosById', newId, 'completed'],
          value: false
        },
        {
          path: ['todos', 'length'],
          value: todoCount + 1
        }
      ];
    }
  },
  todosById: {
    id_0: { label: 'tap dance', completed: false },
    id_1: { label: 'see above', completed: false }
  }
};

const model = new falcor.Model({ source: new LocalDatasource(graph) });


try {
	let n = await model.getValue('todos.length');
	console.log(`1. There are ${n} todos`);

	await model.call(['todos', 'add'], ['dupstep dance party']);

	n = await model.getValue('todos.length');
	console.log(`2. There are ${n} todos`);

	await model.call(['todos', 'add'], ['jumpstyle'],
	                 [[['label', 'completed']]],
	                 [['length']]);

	n = await model.getValue('todos.length');
	console.log(`3. There are ${n} todos`);
	}
catch (err) {
	console.error(err);
	}
} // main()

main();

Now, there is a way to fix this code, i.e. get 2, then 3, then 4 for the number of todos, but I don't think I should need to do this. The fix is to change the first "call" to:

await model.call(['todos', 'add'], ['dupstep dance party'], [], [['length']]);
The way I understand the 4th argument is that it specifies values that I need in the code that uses model.call(), i.e. the code above, and I don't need it since I'm going to make another model.call() immediately after. However, the JavaScript function that implements the "add" operation returns 4 paths that should force the local cache to update its value for todos.length, and it doesn't seem to be doing that.