What's the difference between the 2 "postLink" functions in directive?

Question

From the doc of angularjs, when defining a directive, there's a postLink in compile, and a postLink in link

myModule.directive('directiveName', function factory(injectables) {
  var directiveDefinitionObject = {
    priority: 0,
    template: '<div></div>',
    templateUrl: 'directive.html',
    replace: false,
    transclude: false,
    restrict: 'A',
    scope: false,
    compile: function compile(tElement, tAttrs, transclude) {
      return {
        pre: function preLink(scope, iElement, iAttrs, controller) { ... },
        post: function postLink(scope, iElement, iAttrs, controller) { ... }
      }
    },
    link: function postLink(scope, iElement, iAttrs) { ... }
  };
  return directiveDefinitionObject;
});

What's the difference between them? I notice the postLink in link has a argument less than the one in compile. And are there any other difference?

Solution

They're no different, what you have there is just psuedo-code from the documentation. The postLink function is just the most important one, so there are a variety of ways to declare it.

Here is a Plunker as an example...

... and here is some psuedo code showing the different declarations of a postLink function:

app.directive('dir1', function () {
   return function(scope, elem, attr) {
       //this is the same
   };
});

app.directive('dir2', function () {
   return {
       link: function(scope, elem, attr) {
           //this is the same
       }
   };
});

app.directive('dir3', function () {
   return {
      compile: function compile(tElement, tAttrs, transclude) {
         return {
           post: function postLink(scope, elem, attrs) {
              //this is the same
           }
         }
      }
   };
});

... you only need one.