使用Angular ng-repeat获取数组的最后一个索引

Question

I have an Object that I'm iterating over, that contains array values, here's an example (Note that my version has a lot more information than just content ):

$scope.messages = { "1": [ 
    { "content": "Hello" },
    { "content": "How are you" },
    { "content": "This should be displayed" }
]};

Take this as a "messaging thread" type of scenario, where you would group the threads by a phone number (in this event, 1 ) and then show the last received message (the last index of the array).

Here's what I've tried, but it doesn't work.

<div ng-repeat="(thread_id, message_data) in messages">
    Thread ID: {{thread_id}} <br>
    Last message: {{message_data[message_data.length - 1].content}}
</div>

The thread id shows, but the message data does not.

Hardcoding the value such as:

{{message_data[0].content}}

works as expected.

Before people start suggesting $last please note that $last only returns true or false, depending on if the ng-repeat iteration is on its last cycle. Considering I'm using a (key, value) pair, and in my case the array is the value. I need the array length of the value, which value.length does provide. In this event:

 {{ message_data.length }}

will print out the value of 3 . However using message_data.length - 1 to obtain a value from the array does not work.

Answer 1

Add this to your html

ng-init="$last ? getLastIndex($index) : ''"

Js

$scope.getLastIndex = function (index){
  $scope.lastIndex = index;
}

Then this should work fine

message_data[lastIndex].content

Answer 2

虽然我的确切情况可能并不在所有版本的AngularJS上都存在，但我还是通过在括号内加上数学来解决了该问题。

message_data[(message_data.length - 1)].content