hmpo-model

hmpo-model

• localModel - Simple model for data persistance
• remoteModel - Simple model for interacting with http/rest apis.

Upgrading

The deprecated request library has been replaced with got. The API is very similar, and some args are translated, like auth, and proxy. The new got library doesn't automatically use the proxy environment variables so you would need to use something like global-agent in your app if you need to specify proxies by environment arguments.

The request method no longer takes a body. This should be inserted as json, body, or form into the requestConfig method.

Local Model Usage

constructor(attributes?, options?)

• Local Model extends the Node.JS EventEmitter. The constructor will first call the super constructor of EventEmitter, then assign the options and attributes.
• If no options provided, this will default to an empty object {}.
• attributes is first assigned an empty object without inheriting properties from Object.prototype. e.g. this.attributes = Object.create(null);.
• If attributes are provided then the attributes object is set, with change event notifications suppressed.

get(key)

• Gets a model property via a key.

set(key, value, options?) or set({ key: value }, options?)

• Sets a property on the model to a value and dispatches events.
• Suppresses change event notifications if options.silent is set. e.g. set(key, value, {silent: true}).

unset(fields, options?)

• Unsets a field or fields. fields can be passed as a string or an array. If fields is of type 'string' it will be wrapped in an array with this string as its single element.
• Suppresses change event notifications if options.silent is set. E.g. unset(fields, {silent: true}).

reset(options?)

• Resets a model.
• Suppresses change event notifications if options.silent is set. E.g. reset({silent: true}).

increment(propertyName, amount?)

• Increments a property by the specified amount. Amount defaults to 1 if not provided.

toJSON(bare?)

• Returns a JSON representation of the data in the model.
• Optional paramter bare can be set to true or false. Defaults to false.
• If bare is set to true, the JSON object will have a null prototype and will not inherit object methods from Object.prototype. Helpful info on this can be found on MDN Web Docs.

Remote Model Usage

The Remote Model is a sub-class of the previously highlighted Local Model, and as such inherits its constructor and property accessors.

Normally this would be used as an abstract class and extended with your own implementation.

Implementations would normally define at least a url():url method to define the target of API calls.

Example implimentation:

class MyModel extends HmpoModel {
    url() {
        return super.url('https://my.example.com/url')
    }

    auth() {
        return super.auth('username:password');
    }

    requestConfig(config) {
        config.proxy = 'http://proxy.example.com:3128'
        return super.requestConfig(config);
    }

    // add data to JSON post body
    prepare(callback) {
        super.prepare((err, data) => {
            if (err) return callback(err);
            data.foo = 'bar';
            callback(null, data);
        });
    }

    // transform returned data
    parse(data) {
        data.additionalItem = true;
        return super.parse(data);
    }
}

const model = new MyModel();
model.set('boo', 'baz');
model.save((err, data, responseTime) => {
    if (err) return console.error(err);
    console.log(data);
});

There are three methods for API interaction corresponding to GET, POST, and DELETE http methods:

fetch(args?, callback)

fetch performs a GET request on the url

• If no args passed / function passed as only paramater, then args will be set to undefined.

const model = new Model();
model.fetch((err, data, responseTime) => {
    console.log(data);
});

Request

• Request args for the got library, can be set by overriding the requestConfig({}):{} method.

• The url can be configured either by setting a default in the model options or requestConfig() data, or by overriding the url(default, args):url method.

• proxy, timeout, and basic auth can be set in the same way, using model options, setting in requestConfig(), or by overriding a method.

• Specifying a proxy will set up a proxy tunneling agent for the request.

• Specifying a numeric timeout will set the same timeout for all got timeout values.

• Basic auth can be a colon separated string, or a {username, password} or {user, pass} object.

Response

• The returned body will be expected to be in JSON format.
• If statusCode < 400 the JSON response will be set to the model. This behaviour can be changed by overriding the parse(data):data method.
• If statusCode >= 400 the data will be passed to the parseError(statusCode, data):error method, and the fetch callback will be called with the returned error.
• If response statuses need to be treated differently than the above, the parseResponse(statusCode, data, cb) method can be overridden.
• If the response body is not going to be JSON, the handleResponse(response, cb) method can be overridden.

save(args?, callback)

save performs a POST request on the url

• If no args passed / function passed as only paramater, then args will be set to undefined.

const model = new Model();
model.set({
    property: 'properties are sent as JSON request body by default'
});
model.save((err, data, responseTime) => {
    console.log(data);
});

• By default the post body will be a JSON encoded object containing all attributes set to the model using, extracted using model.toJSON(). This behaviour can be changed by overriding the prepare(callback(err, data)) method.
• The response and body will be treated the same way as the fetch request above.

delete(args?, callback)

delete performs a DELETE request on the url

• If no args passed / function passed as only paramater, then args will be set to undefined.

const model = new Model();
model.delete((err, data, responseTime) => {
    console.log(data);
});

Events

API requests will emit events as part of their lifecycle.

sync is emitted when an API request is sent

model.on('sync', function (settings) { });

success is emitted when an API request successfully completes

model.on('success', function (data, settings, statusCode, responseTime) { });

fail is emitted when an API request fails

model.on('fail', function (err, data, settings, statusCode, responseTime) { });

Hooks

API requests will fire hooks specified in model options as part of their lifecycle.

new Model(null, options);

sync hook is fired when an API request is sent

options.hooks.sync({ settings });

success hook is fired when an API request successfully completes

options.hooks.success({ data, settings, statusCode, responseTime });

fail hook is fired when an API request fails

options.hooks.fail({ err, data, settings, statusCode, responseTime });

Examples in other apps

hmpo-form-wizard example : Submit Model hmpo-app example : Submission Model