mithril-postgrest

mithril-postgrest

Use cases

What this library is supposed to do:

• Help you authenticating in a PostgREST server.
• Provide wrappers arround the mithril request function to use JWT.
• Provide a constructor for objects that will interact with PostgREST endpoints
• Provide some helpers to build some useful View-Model objects.

Usage

First we should init the library so that it will build the functions to access the API. The init function takes one argument which is the API endpoint prefix, containing the URI to which all addresses will be appended. If the API is being served from exactly the same location as the page running the JS you can just initialize without any argument.

To use an API available at http://api.foo.com/v1 you can use the code:

postgrest.init(
  "http://api.foo.com/v1",
  {method: "GET", url: "/authentication_endpoint"}
);

This will create three functions:

• postgrest.request - which should be used for anonymous API calls.
• postgrest.requestWithToken - which should be used for authenticated API calls.
• postgrest.model - creates an object that abstracts an API endpoint

Both request functions are just proxies for mithril's m.request and will return in the same fashion.

However, the postgrest.requestWithToken stores the JWT for api authentication in a public getter: postgrest.token.

This token can be manipulated to implement session storage for the authentication token.

Models

To generate a model you should call the model function passing its name. The name of the model should be the name of the endpoint in the PostgREST server.

For example, the following code:

var users = postgrest.model('users');

will generate an object with functions to operate the /users endpoint. To get one record from the users table you could use:

var users = postgrest.model('users');
users.getRow({id: 'eq.1'}).then(function(row){
	console.log('fecthed:', row);
});

Now if you don't want to fetch data as anonymous, and prefer to use your authentication token:

var users = postgrest.model('users');
users.getRowWithToken({id: 'eq.1'}).then(function(row){
	console.log('fecthed:', row);
});

When updating, the model always fetches the updated record by default:

var users = postgrest.model('users');
users.patchWithToken({id: 'eq.1'}, {name: 'new name'}).then(function(row){
	console.log('updated:', row);
});

The model will have the following property once it is created:

• pageSize - defines the size of each page that comes in getPage call. Default is 10.

View-Models

There are some commom View-Model objects that can be generated automaticaly.

filtersVM

One of such cases is the filters VM. It is used to bind a HTML form to a set of getter/setter functions that will be used to generate a query string. You can use the function:

• filtersVM(attributes) - Generate a View-Model based on the attributes object (maps names to operators).

As in the example:

var filters = postgrest.filtersVM({id: 'eq'});
var users = postgrest.model('users');
users.getPage(filters.id(7).parameters()).then(function(data){
	console.log('fetched:', data);
});

The filters.parameters() will return an object that can be fed directly to a request with filters and the order by.

If you want to apply any transformation to the value before it being fed to the parameters() function you have a toFilter function that has been created in each property for you. So let's say we want to remove diacriticts from the name before sending the string:

filters.name.toFilter = function(){
  return removeDiacritics(this());
};

Assuming that you have a removeDiacritics function defined within the scope of the above code, once you call the parameters() this function will be applied to the property.

paginationVM

Another View-Model very convenient is one that can paginate a model and fetch pages from the API. To create such an object you can call:

 var paginator = paginationVM(model, order, authenticate)

This would generate a pagination View-Model that loads pages using the given model, applying the order to the request. The third parameter is a boolean to choose between a getPage (passing false) or getPageWithToken (passing true, this is the default).

This can be used with the model and filters defined above like:

var userPages = postgrest.paginationVM(users);
// The firstPage function returns a mithril promise
userPages.firstPage(filters.parameters()).then(function(){
  // Results are in collection
  console.log(userPages.collection());
},
function(){
    alert('Error loading users');
});

After the first call to .firstPage the parameters are stored for use in next pages. To change the filters you need to call .firstPage again.

// The nextPage function returns a mithril promise
userPages.nextPage().then(function(){
  // Results are appended to collection
  console.log(userPages.collection());
},
function(){
    alert('Error loading next page');
});