AngularJS ng-bind with a function

问题:

I want to show a table format for the Attachments section. I have the lookup and results data. Both have a common column of attachmentTypeId. I want to show the attachment category description based on the id. In the ng-bind I tried an attempt, it's not worked.

I am using a function in the ng-bind, hope the approach is wrong, expect an alternate for the approach.

The attachmentLookup contains the attachmentDesc, attachmentTypeId

  $scope.attachmentLookup = [{
    "attachmentDesc": "Category One",
    "attachmentTypeId": "1"
  }, {
    "attachmentDesc": "Category Two",
    "attachmentTypeId": "2"
  }, {
    "attachmentDesc": "Category Three",
    "attachmentTypeId": "3"
  }, {
    "attachmentDesc": "Category Four",
    "attachmentTypeId": "4"
  }, {
    "attachmentDesc": "Category Five",
    "attachmentTypeId": "5"
  }];

And the attachmentDetails data from the database as,

  $scope.attachmentDetails = [{
    "attachmentId": "001",
    "fileName": "File Name 001",
    "attachmentTypeId": "1"
  }, {
    "attachmentId": "003",
    "fileName": "File Name 003",
    "attachmentTypeId": "2"
  }, {
    "attachmentId": "005",
    "fileName": "File Name 005",
    "attachmentTypeId": "3"
  }, {
    "attachmentId": "007",
    "fileName": "File Name 007",
    "attachmentTypeId": "1"
  }, {
    "attachmentId": "009",
    "fileName": "File Name 009",
    "attachmentTypeId": "2"
  }, {
    "attachmentId": "011",
    "fileName": "File Name 011",
    "attachmentTypeId": "3"
  }];

The HTML code as,

<table>
  <thead>
    <tr>
      <th>File Name</th>
      <th>|</th>
      <th>Category</th>
    </tr>
  </thead>
  <tbody>
    <tr ng-repeat="attachment in attachmentDetails">
      <td> <span ng-bind="attachment.fileName"></span>
      </td>
      <td>|</td>
      <td> <span ng-bind="getCatgoryName(attachment.attachmentTypeId)"></span>
      </td>
    </tr>
  </tbody>
</table>

And the getCatgoryName code from the controller is,

$scope.getCatgoryName = function (attachmentTypeId) {
    angular.forEach($scope.attachmentLookup, function (attachemnt) {
        if (attachemnt.attachmentTypeId === attachmentTypeId)
            return attachemnt.attachmentDesc;
    });
};

Sample Plunker: http://plnkr.co/edit/dZy5gW4q9CxWF2NszXYc

回答1:

The brackets are dirty checked, therefore the function will be called for every $digest.

This ng-bind is a directive, it will use a watcher on what is being passed to ng-bind.

Therefore, ng-bind will only apply, when the passed variable or value does actually change.

With a function, you are not passing a variable, therefore it will not fire for every $digest.

It is therefore, better to use brackets with a function call.

I have updated the plunker here: http://plnkr.co/edit/LHC2IZ0Qk9LOOYsjrjaf?p=preview

I have changed the HTML here:

<tr ng-repeat="a in attachmentDetails">
    <td> <span>{{a.fileName}}</span></td>
    <td>|</td>
    <td> {{ getCatgoryName(a.attachmentTypeId) }}</td>
</tr>

The function has also been modified:

  $scope.getCatgoryName = function(attachmentTypeId) {
    var desc = "";
    angular.forEach($scope.attachmentLookup, function(attachemnt) {
      if (parseInt(attachemnt.attachmentTypeId) == attachmentTypeId)
        desc = attachemnt.attachmentDesc;
    });

    return desc;
  };

回答2:

The another way to do the same thing is like below:

<tr ng-repeat="delivery in deliveries">
<td>{{delivery.pickup}}</td>
<td>{{delivery.destination}}</td>
<td>{{getVehicleDescription(delivery) || (delivery.isVehicleDescription ? delivery.modelType : delivery.vehicleType)}}</td></tr>

Controller function has also been modified in this way:

$scope.getVehicleDescription = function(delivery){
        $scope.roads.map(function(road){
            if(road.modelTypeID == delivery.vehicleType && !delivery.isVehicleDescription){
                delivery.modelType = road.modelType;
                delivery.isVehicleDescription = true;
            }
        })
    };