Function initializeDirectiveBindings

lib/test/angular/1.4.3/angular.js:8659–8758

(scope, attrs, destination, bindings,
                                         directive, newScope)

    // Set up $watches for isolate scope and controller bindings. This process
    // only occurs for isolate scopes and new scopes with controllerAs.
    function initializeDirectiveBindings(scope, attrs, destination, bindings,
                                         directive, newScope) {
      var onNewScopeDestroyed;
      forEach(bindings, function(definition, scopeName) {
        var attrName = definition.attrName,
        optional = definition.optional,
        mode = definition.mode, // @, =, or &
        lastValue,
        parentGet, parentSet, compare;

        if (!hasOwnProperty.call(attrs, attrName)) {
          // In the case of user defined a binding with the same name as a method in Object.prototype but didn't set
          // the corresponding attribute. We need to make sure subsequent code won't access to the prototype function
          attrs[attrName] = undefined;
        }

        switch (mode) {

          case '@':
            if (!attrs[attrName] && !optional) {
              destination[scopeName] = undefined;
            }

            attrs.$observe(attrName, function(value) {
              destination[scopeName] = value;
            });
            attrs.$$observers[attrName].$$scope = scope;
            if (attrs[attrName]) {
              // If the attribute has been provided then we trigger an interpolation to ensure
              // the value is there for use in the link fn
              destination[scopeName] = $interpolate(attrs[attrName])(scope);
            }
            break;

          case '=':
            if (optional && !attrs[attrName]) {
              return;
            }
            parentGet = $parse(attrs[attrName]);

            if (parentGet.literal) {
              compare = equals;
            } else {
              compare = function(a, b) { return a === b || (a !== a && b !== b); };
            }
            parentSet = parentGet.assign || function() {
              // reset the change, or we will throw this exception on every $digest
              lastValue = destination[scopeName] = parentGet(scope);
              throw $compileMinErr('nonassign',
                  "Expression '{0}' used with directive '{1}' is non-assignable!",
                  attrs[attrName], directive.name);
            };
            lastValue = destination[scopeName] = parentGet(scope);
            var parentValueWatch = function parentValueWatch(parentValue) {
              if (!compare(parentValue, destination[scopeName])) {
                // we are out of sync and need to copy
                if (!compare(parentValue, lastValue)) {
                  // parent changed and it has precedence