Cyclic dependency using Knockout subscribe

Question

Is there any possible fix to the below code where I face cyclic dependency using Knockout.js subscribe.

this.observable1.subscribe(function(value){
self.observable2("someValue");
});

this.observable2.subscribe(function(value){
self.observable1("someValue");
});

Where "self" is an alias to "this" and observable1 linked to combo box, and observable2 linked to date picker.

Kindly suggest

Understanding why the combobox must affect the datepicker and vice versa may help in providing alternative solutions. Can you provide that reasoning? — Origineil, Jun 27 '14 at 13:59
@Origineil, When I set combo box value to "time-period", datepicker has to populate date as per the time-period value (ex., current month) and when I edit Date field which is associated with date-picker, "time-period" has to change automatically to "custom". — Venkat, Jun 30 '14 at 11:56
You can use computed for this. Checkout this answer: https://stackoverflow.com/a/22694205 — Nandish, Jul 23 '18 at 11:25

score 1 · Accepted Answer · answered Jun 28 '14 at 08:51

As @Origineil said, you probably need to re-think your solution.

But if you really want to keep current solution, you could use a flag to break the cycle.

var isInnerUpdate = false;

this.observable1.subscribe(function(value){
  if (isInnerUpdate) {
    isInnerUpdate = false;
  } else {
    isInnerUpdate = true;
    self.observable2("someValue");
  }
});

this.observable2.subscribe(function(value){
    if (isInnerUpdate) {
    isInnerUpdate = false;
  } else {
    isInnerUpdate = true;
    self.observable1("someValue");
  }
});

Venkat · Answer 2 · 2014-06-30T12:46:21.160

0

I have used a global variable and logic as below and it worked fine for me,

var enableSubcribe = false; //global variable 
this.observable1.subscribe(function(value){ 
enableSubcribe = true; 
self.observable2("someValue");
enableSubcribe = false; 
}); 

this.observable2.subscribe(function(value){
 if(!enableSubcribe ){
self.observable1("someValue");
}
 });

Thanks to Huocp, your logic looks like works as well. Thanks all for your comments and answer.

edited Jun 30 '14 at 12:46

answered Jun 30 '14 at 12:40

Venkat

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Not sure if you noticed, your enableSubscribe is not a global variable, it is a variable only visible in the function scope of your viewmodel constructor function. – huocp Jul 01 '14 at 09:04
sorry for that, the global variable has to be declared as this.enableSubcribe = ko.observable(); in the constructor. – Venkat Jul 07 '14 at 12:00

Cyclic dependency using Knockout subscribe

2 Answers2