te')); return $arr; } /* 遍历用户所有主题 * @param $uid 用户ID * @param int $page 页数 * @param int $pagesize 每页记录条数 * @param bool $desc 排序方式 TRUE降序 FALSE升序 * @param string $key 返回的数组用那一列的值作为 key * @param array $col 查询哪些列 */ function thread_tid_find_by_uid($uid, $page = 1, $pagesize = 1000, $desc = TRUE, $key = 'tid', $col = array()) { if (empty($uid)) return array(); $orderby = TRUE == $desc ? -1 : 1; $arr = thread_tid__find($cond = array('uid' => $uid), array('tid' => $orderby), $page, $pagesize, $key, $col); return $arr; } // 遍历栏目下tid 支持数组 $fid = array(1,2,3) function thread_tid_find_by_fid($fid, $page = 1, $pagesize = 1000, $desc = TRUE) { if (empty($fid)) return array(); $orderby = TRUE == $desc ? -1 : 1; $arr = thread_tid__find($cond = array('fid' => $fid), array('tid' => $orderby), $page, $pagesize, 'tid', array('tid', 'verify_date')); return $arr; } function thread_tid_delete($tid) { if (empty($tid)) return FALSE; $r = thread_tid__delete(array('tid' => $tid)); return $r; } function thread_tid_count() { $n = thread_tid__count(); return $n; } // 统计用户主题数 大数量下严谨使用非主键统计 function thread_uid_count($uid) { $n = thread_tid__count(array('uid' => $uid)); return $n; } // 统计栏目主题数 大数量下严谨使用非主键统计 function thread_fid_count($fid) { $n = thread_tid__count(array('fid' => $fid)); return $n; } ?>javascript - Access Outside Variable inside a internal function typescript - Stack Overflow

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    javascript - Access Outside Variable inside a internal function typescript - Stack Overflow

    programmeradmin4浏览0评论

    I have one variable outside a function that I need to change the value. I normally use "this" to access the variable but at that point of the code, "this" is not reachable. 

    export class GamesDetailPage {

  details : any = {};
  type : String;
  level : Number; 
  cards : any = {}; // THE VARIABLE I WANT TO SET THE VALUE


  constructor(public navCtrl: NavController, public http: HttpClient , private device: Device, private serviceProvider: ServicesProvider,     
                                            public navParams: NavParams
) {
    this.type = navParams.get('gameType');
    this.level = navParams.get('gameLevel');
  }

  ionViewDidLoad() {


    this.getCards();  // WHERE I CALL THE METHOD  
  }


  getCards(){
    var deviceUUID = this.device.uuid;
    var platform =  this.device.platform;
    var cardsReq = {"gameType": this.type ,"gameLevel": this.level};
    var dialog = this.dialogs;

   this.serviceProvider.getCards(deviceUUID, platform, cardsReq)

    .then(function (res){
      this.cards = res;// HERE I WANT TO SET THE VARIABLE BUT "THIS" IS UNDEFINED
    })
    .catch(function(err){
      console.log("Error");
    })
  }
}

    I have one variable outside a function that I need to change the value. I normally use "this" to access the variable but at that point of the code, "this" is not reachable. 

    export class GamesDetailPage {

  details : any = {};
  type : String;
  level : Number; 
  cards : any = {}; // THE VARIABLE I WANT TO SET THE VALUE


  constructor(public navCtrl: NavController, public http: HttpClient , private device: Device, private serviceProvider: ServicesProvider,     
                                            public navParams: NavParams
) {
    this.type = navParams.get('gameType');
    this.level = navParams.get('gameLevel');
  }

  ionViewDidLoad() {


    this.getCards();  // WHERE I CALL THE METHOD  
  }


  getCards(){
    var deviceUUID = this.device.uuid;
    var platform =  this.device.platform;
    var cardsReq = {"gameType": this.type ,"gameLevel": this.level};
    var dialog = this.dialogs;

   this.serviceProvider.getCards(deviceUUID, platform, cardsReq)

    .then(function (res){
      this.cards = res;// HERE I WANT TO SET THE VARIABLE BUT "THIS" IS UNDEFINED
    })
    .catch(function(err){
      console.log("Error");
    })
  }
}
    • javascript
    • typescript
    Share Improve this question edited Feb 20, 2018 at 8:53 marionebl 3,39222 silver badges34 bronze badges asked Feb 20, 2018 at 8:52 Vinicius MartinVinicius Martin 1891 gold badge4 silver badges15 bronze badges 1
    • Possible duplicate of How to access the correct `this` inside a callback? – marionebl Commented Feb 20, 2018 at 8:54
    Add a ment  | 

    3 Answers 3

    Reset to default 5

    Here you need to use ES6 arrow function as in the earlier (function(){ method this does not refer to the class but in the es6 one it will...

    An arrow function expression has a shorter syntax than a function expression and does not have its own this

    .then( 
(res) => {
      this.cards = res; // Should work now
    }
)

    Because the outter this is shadowed by this of the function. The most straight forward way and also the remend way is to use arrow function in typescript.

    Change the lambda function to:

    (res) => {}

    Another old solution is save this to a temp variable:

    that = this

    and then access that inside your lambda function.

    In JavaScript this relates to the current function. TypeScript just hides this fact when it transpiles your code.

    As a result, there are two things you can do.

    First you could use ES6 arrow functions (TypeScript will do the this scoping for you)

    .then((res) => {
    this.cards = res;
})

    Alternatively you could handle it yourself

    getCards(){
    var _this = this;

    // More code

    .then(function (res){
        _this.cards = res;
    })

    If you check the transpiled output for both cases they should be almost the same

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