ngModel doesnt´t work fine with select tag and Class instances in Angulardart 5











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In a select tag, I need two-way binding, but is not working.



<select [(ngModel)]="selectedCountry">
<option *ngFor="let country of countries" [ngValue]="country">
{{country.name}}
</option>
</select>




  • selectedCountry is a Country instance: selectedCountry.id = 3


  • countries is a Country instance List: country1.id = 1, country3.id = 3, country3.id = 3


selectedCountry and country3 have equal values but they aren't the same instance. Then country3 option is not selected.



I have overwritten the equality (==) operator and hashCode for the Country class, but it still does not work.



What's the problem? Is there something similar to the angular compareWith directive?



<select [compareWith]="equals"  [(ngModel)]="selectedCountry">
<option *ngFor="let country of countries" [ngValue]="country">
{{country.name}}
</option>
</select>




equals(o1: Country, o2: Country) {
return o1.id === o2.id;
}









share|improve this question
























  • [(ngModel)]="selectedCountries" sounds wrong. There can only be one value be selected. What type is selectedCountries and what value does it contain? What does "doesnt´t work fine" mean exactly?
    – Günter Zöchbauer
    Nov 8 at 9:07










  • Instead of implementing operator== (which is usually a good idea anyway) you can also use webdev.dartlang.org/angular/guide/…
    – Günter Zöchbauer
    Nov 8 at 9:10










  • selectedCountry is a class instance and countries list has a class instance with equals property values, but no option is selected.
    – rafbermudez
    Nov 8 at 9:20










  • Try trackBy. I haven't found anything about compareWith. Where did you get that from?
    – Günter Zöchbauer
    Nov 8 at 9:22










  • compareWith directive is not a core angular directive: github.com/angular/angular/pull/13349
    – rafbermudez
    Nov 8 at 9:45















up vote
0
down vote

favorite












In a select tag, I need two-way binding, but is not working.



<select [(ngModel)]="selectedCountry">
<option *ngFor="let country of countries" [ngValue]="country">
{{country.name}}
</option>
</select>




  • selectedCountry is a Country instance: selectedCountry.id = 3


  • countries is a Country instance List: country1.id = 1, country3.id = 3, country3.id = 3


selectedCountry and country3 have equal values but they aren't the same instance. Then country3 option is not selected.



I have overwritten the equality (==) operator and hashCode for the Country class, but it still does not work.



What's the problem? Is there something similar to the angular compareWith directive?



<select [compareWith]="equals"  [(ngModel)]="selectedCountry">
<option *ngFor="let country of countries" [ngValue]="country">
{{country.name}}
</option>
</select>




equals(o1: Country, o2: Country) {
return o1.id === o2.id;
}









share|improve this question
























  • [(ngModel)]="selectedCountries" sounds wrong. There can only be one value be selected. What type is selectedCountries and what value does it contain? What does "doesnt´t work fine" mean exactly?
    – Günter Zöchbauer
    Nov 8 at 9:07










  • Instead of implementing operator== (which is usually a good idea anyway) you can also use webdev.dartlang.org/angular/guide/…
    – Günter Zöchbauer
    Nov 8 at 9:10










  • selectedCountry is a class instance and countries list has a class instance with equals property values, but no option is selected.
    – rafbermudez
    Nov 8 at 9:20










  • Try trackBy. I haven't found anything about compareWith. Where did you get that from?
    – Günter Zöchbauer
    Nov 8 at 9:22










  • compareWith directive is not a core angular directive: github.com/angular/angular/pull/13349
    – rafbermudez
    Nov 8 at 9:45













up vote
0
down vote

favorite









up vote
0
down vote

favorite











In a select tag, I need two-way binding, but is not working.



<select [(ngModel)]="selectedCountry">
<option *ngFor="let country of countries" [ngValue]="country">
{{country.name}}
</option>
</select>




  • selectedCountry is a Country instance: selectedCountry.id = 3


  • countries is a Country instance List: country1.id = 1, country3.id = 3, country3.id = 3


selectedCountry and country3 have equal values but they aren't the same instance. Then country3 option is not selected.



I have overwritten the equality (==) operator and hashCode for the Country class, but it still does not work.



What's the problem? Is there something similar to the angular compareWith directive?



<select [compareWith]="equals"  [(ngModel)]="selectedCountry">
<option *ngFor="let country of countries" [ngValue]="country">
{{country.name}}
</option>
</select>




equals(o1: Country, o2: Country) {
return o1.id === o2.id;
}









share|improve this question















In a select tag, I need two-way binding, but is not working.



<select [(ngModel)]="selectedCountry">
<option *ngFor="let country of countries" [ngValue]="country">
{{country.name}}
</option>
</select>




  • selectedCountry is a Country instance: selectedCountry.id = 3


  • countries is a Country instance List: country1.id = 1, country3.id = 3, country3.id = 3


selectedCountry and country3 have equal values but they aren't the same instance. Then country3 option is not selected.



I have overwritten the equality (==) operator and hashCode for the Country class, but it still does not work.



What's the problem? Is there something similar to the angular compareWith directive?



<select [compareWith]="equals"  [(ngModel)]="selectedCountry">
<option *ngFor="let country of countries" [ngValue]="country">
{{country.name}}
</option>
</select>




equals(o1: Country, o2: Country) {
return o1.id === o2.id;
}






dart angular-dart






share|improve this question















share|improve this question













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edited Nov 8 at 10:22









Günter Zöchbauer

308k64911860




308k64911860










asked Nov 8 at 8:58









rafbermudez

113




113












  • [(ngModel)]="selectedCountries" sounds wrong. There can only be one value be selected. What type is selectedCountries and what value does it contain? What does "doesnt´t work fine" mean exactly?
    – Günter Zöchbauer
    Nov 8 at 9:07










  • Instead of implementing operator== (which is usually a good idea anyway) you can also use webdev.dartlang.org/angular/guide/…
    – Günter Zöchbauer
    Nov 8 at 9:10










  • selectedCountry is a class instance and countries list has a class instance with equals property values, but no option is selected.
    – rafbermudez
    Nov 8 at 9:20










  • Try trackBy. I haven't found anything about compareWith. Where did you get that from?
    – Günter Zöchbauer
    Nov 8 at 9:22










  • compareWith directive is not a core angular directive: github.com/angular/angular/pull/13349
    – rafbermudez
    Nov 8 at 9:45


















  • [(ngModel)]="selectedCountries" sounds wrong. There can only be one value be selected. What type is selectedCountries and what value does it contain? What does "doesnt´t work fine" mean exactly?
    – Günter Zöchbauer
    Nov 8 at 9:07










  • Instead of implementing operator== (which is usually a good idea anyway) you can also use webdev.dartlang.org/angular/guide/…
    – Günter Zöchbauer
    Nov 8 at 9:10










  • selectedCountry is a class instance and countries list has a class instance with equals property values, but no option is selected.
    – rafbermudez
    Nov 8 at 9:20










  • Try trackBy. I haven't found anything about compareWith. Where did you get that from?
    – Günter Zöchbauer
    Nov 8 at 9:22










  • compareWith directive is not a core angular directive: github.com/angular/angular/pull/13349
    – rafbermudez
    Nov 8 at 9:45
















[(ngModel)]="selectedCountries" sounds wrong. There can only be one value be selected. What type is selectedCountries and what value does it contain? What does "doesnt´t work fine" mean exactly?
– Günter Zöchbauer
Nov 8 at 9:07




[(ngModel)]="selectedCountries" sounds wrong. There can only be one value be selected. What type is selectedCountries and what value does it contain? What does "doesnt´t work fine" mean exactly?
– Günter Zöchbauer
Nov 8 at 9:07












Instead of implementing operator== (which is usually a good idea anyway) you can also use webdev.dartlang.org/angular/guide/…
– Günter Zöchbauer
Nov 8 at 9:10




Instead of implementing operator== (which is usually a good idea anyway) you can also use webdev.dartlang.org/angular/guide/…
– Günter Zöchbauer
Nov 8 at 9:10












selectedCountry is a class instance and countries list has a class instance with equals property values, but no option is selected.
– rafbermudez
Nov 8 at 9:20




selectedCountry is a class instance and countries list has a class instance with equals property values, but no option is selected.
– rafbermudez
Nov 8 at 9:20












Try trackBy. I haven't found anything about compareWith. Where did you get that from?
– Günter Zöchbauer
Nov 8 at 9:22




Try trackBy. I haven't found anything about compareWith. Where did you get that from?
– Günter Zöchbauer
Nov 8 at 9:22












compareWith directive is not a core angular directive: github.com/angular/angular/pull/13349
– rafbermudez
Nov 8 at 9:45




compareWith directive is not a core angular directive: github.com/angular/angular/pull/13349
– rafbermudez
Nov 8 at 9:45












2 Answers
2






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up vote
0
down vote













Is there something similar to the angular compareWith directive?



You can use trackBy https://webdev.dartlang.org/angular/guide/template-syntax#ngfor-with-trackby



Object trackByCountryId(_, dynamic o) => o is Country ? o.id : o;




<select *ngFor="let hero of heroes; trackBy: trackByCountryId" [(ngModel)]="selectedCountry">
<option *ngFor="let country of countries" [ngValue]="country">
{{country.name}}
</option>
</select>





share|improve this answer





















  • This is useful when the list of countries is changing but it does not solve my problem
    – rafbermudez
    Nov 8 at 14:01










  • No idea what you are talking about. That exactly to solve the issue your question is about. I don't know what you mean with "when the list of countries is changing". I don't see that related.
    – Günter Zöchbauer
    Nov 8 at 14:13


















up vote
0
down vote













I found the problem:



The use of the identical() function to compare values in select_control_value_accessor of the select ngModel instead ==.



I opened a github issue:
https://github.com/dart-lang/angular/issues/1659



Meanwhile, I'm not using two-way binding complex object:



<select [(ngModel)]="selectedCountryId">
<option *ngFor="let country of countries" [ngValue]="country.id">
{{country.name}}
</option>
</select>





share|improve this answer





















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    2 Answers
    2






    active

    oldest

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    2 Answers
    2






    active

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    up vote
    0
    down vote













    Is there something similar to the angular compareWith directive?



    You can use trackBy https://webdev.dartlang.org/angular/guide/template-syntax#ngfor-with-trackby



    Object trackByCountryId(_, dynamic o) => o is Country ? o.id : o;




    <select *ngFor="let hero of heroes; trackBy: trackByCountryId" [(ngModel)]="selectedCountry">
    <option *ngFor="let country of countries" [ngValue]="country">
    {{country.name}}
    </option>
    </select>





    share|improve this answer





















    • This is useful when the list of countries is changing but it does not solve my problem
      – rafbermudez
      Nov 8 at 14:01










    • No idea what you are talking about. That exactly to solve the issue your question is about. I don't know what you mean with "when the list of countries is changing". I don't see that related.
      – Günter Zöchbauer
      Nov 8 at 14:13















    up vote
    0
    down vote













    Is there something similar to the angular compareWith directive?



    You can use trackBy https://webdev.dartlang.org/angular/guide/template-syntax#ngfor-with-trackby



    Object trackByCountryId(_, dynamic o) => o is Country ? o.id : o;




    <select *ngFor="let hero of heroes; trackBy: trackByCountryId" [(ngModel)]="selectedCountry">
    <option *ngFor="let country of countries" [ngValue]="country">
    {{country.name}}
    </option>
    </select>





    share|improve this answer





















    • This is useful when the list of countries is changing but it does not solve my problem
      – rafbermudez
      Nov 8 at 14:01










    • No idea what you are talking about. That exactly to solve the issue your question is about. I don't know what you mean with "when the list of countries is changing". I don't see that related.
      – Günter Zöchbauer
      Nov 8 at 14:13













    up vote
    0
    down vote










    up vote
    0
    down vote









    Is there something similar to the angular compareWith directive?



    You can use trackBy https://webdev.dartlang.org/angular/guide/template-syntax#ngfor-with-trackby



    Object trackByCountryId(_, dynamic o) => o is Country ? o.id : o;




    <select *ngFor="let hero of heroes; trackBy: trackByCountryId" [(ngModel)]="selectedCountry">
    <option *ngFor="let country of countries" [ngValue]="country">
    {{country.name}}
    </option>
    </select>





    share|improve this answer












    Is there something similar to the angular compareWith directive?



    You can use trackBy https://webdev.dartlang.org/angular/guide/template-syntax#ngfor-with-trackby



    Object trackByCountryId(_, dynamic o) => o is Country ? o.id : o;




    <select *ngFor="let hero of heroes; trackBy: trackByCountryId" [(ngModel)]="selectedCountry">
    <option *ngFor="let country of countries" [ngValue]="country">
    {{country.name}}
    </option>
    </select>






    share|improve this answer












    share|improve this answer



    share|improve this answer










    answered Nov 8 at 10:25









    Günter Zöchbauer

    308k64911860




    308k64911860












    • This is useful when the list of countries is changing but it does not solve my problem
      – rafbermudez
      Nov 8 at 14:01










    • No idea what you are talking about. That exactly to solve the issue your question is about. I don't know what you mean with "when the list of countries is changing". I don't see that related.
      – Günter Zöchbauer
      Nov 8 at 14:13


















    • This is useful when the list of countries is changing but it does not solve my problem
      – rafbermudez
      Nov 8 at 14:01










    • No idea what you are talking about. That exactly to solve the issue your question is about. I don't know what you mean with "when the list of countries is changing". I don't see that related.
      – Günter Zöchbauer
      Nov 8 at 14:13
















    This is useful when the list of countries is changing but it does not solve my problem
    – rafbermudez
    Nov 8 at 14:01




    This is useful when the list of countries is changing but it does not solve my problem
    – rafbermudez
    Nov 8 at 14:01












    No idea what you are talking about. That exactly to solve the issue your question is about. I don't know what you mean with "when the list of countries is changing". I don't see that related.
    – Günter Zöchbauer
    Nov 8 at 14:13




    No idea what you are talking about. That exactly to solve the issue your question is about. I don't know what you mean with "when the list of countries is changing". I don't see that related.
    – Günter Zöchbauer
    Nov 8 at 14:13












    up vote
    0
    down vote













    I found the problem:



    The use of the identical() function to compare values in select_control_value_accessor of the select ngModel instead ==.



    I opened a github issue:
    https://github.com/dart-lang/angular/issues/1659



    Meanwhile, I'm not using two-way binding complex object:



    <select [(ngModel)]="selectedCountryId">
    <option *ngFor="let country of countries" [ngValue]="country.id">
    {{country.name}}
    </option>
    </select>





    share|improve this answer

























      up vote
      0
      down vote













      I found the problem:



      The use of the identical() function to compare values in select_control_value_accessor of the select ngModel instead ==.



      I opened a github issue:
      https://github.com/dart-lang/angular/issues/1659



      Meanwhile, I'm not using two-way binding complex object:



      <select [(ngModel)]="selectedCountryId">
      <option *ngFor="let country of countries" [ngValue]="country.id">
      {{country.name}}
      </option>
      </select>





      share|improve this answer























        up vote
        0
        down vote










        up vote
        0
        down vote









        I found the problem:



        The use of the identical() function to compare values in select_control_value_accessor of the select ngModel instead ==.



        I opened a github issue:
        https://github.com/dart-lang/angular/issues/1659



        Meanwhile, I'm not using two-way binding complex object:



        <select [(ngModel)]="selectedCountryId">
        <option *ngFor="let country of countries" [ngValue]="country.id">
        {{country.name}}
        </option>
        </select>





        share|improve this answer












        I found the problem:



        The use of the identical() function to compare values in select_control_value_accessor of the select ngModel instead ==.



        I opened a github issue:
        https://github.com/dart-lang/angular/issues/1659



        Meanwhile, I'm not using two-way binding complex object:



        <select [(ngModel)]="selectedCountryId">
        <option *ngFor="let country of countries" [ngValue]="country.id">
        {{country.name}}
        </option>
        </select>






        share|improve this answer












        share|improve this answer



        share|improve this answer










        answered Nov 8 at 14:13









        rafbermudez

        113




        113






























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