I want to use [(ngModel)] for a nested object, but is giving me an error
Cannot read property 'mxn' of undefined
these are the data structure of my models:
company.model.ts
import Currency from './currency.model';
class Company {
_id: string;
name: string;
maxLimit: number;
source: [string];
deliveryMethod: [string];
currency: Currency;
date: Date;
constructor() {
this.name = '';
this.date = new Date();
this.maxLimit = 0;
this.source = [''];
this.deliveryMethod = [''];
this.currency.mxn = 0;
this.currency.php = 0;
}
}
export default Company;
currency.model.ts
class Currency {
mxn: number;
php: number;
constructor() {
this.mxn = 0;
this.php = 0;
}
}
export default Currency;
and this is part of company.ts
public newCompany: Company = new Company();
companiesList: Company[];
editcompanies: Company[] = [];
and HTML
in HTML page I'm able to show the mxn
value by just using :
<tr class="companies" *ngFor="let company of companiesList">
{{company.currency.mxn}}
but when I want to use it with ngModel
two-way binding for updating the value and sending it to the database it doesn't work.
[(ngModel)] = "newCompany.currency.mxn"
it produces the mentioned error above. if I use [(ngModel)] = "newCompany.currency"
it doesn't give me an error but the code it's useless since i can't assign any value to mxn
.
I have to say that [(ngModel)] = "newCompany.name"
it works fine with this and I can update the name.
the backend works fine as I tried it with Postman. the problem is angular side.
so the question is if my data structure is correct how can I use two-way binding for the nested object?
currency: Currency;
...
constructor() {
...
this.currency.mxn = 0;
this.currency.php = 0;
}
mxn and php do not exist yet until you instantiate an instance of Currency
. The instance currency
is null. It doesn't contain any properties.
currency: Currency;
...
constructor() {
...
this.currency = new Currency(); // invoke Currency constructor, create mxn and php with value 0, therefore you dont need this.currency.mxn = 0 and same to php
}
A slight change in your Company model should be enough:
class Company { _id: string; name: string; maxLimit: number; source: [string]; deliveryMethod: [string]; currency: Currency = new Currency(); // provide an instance, otherwise this field will be undefined date: Date; constructor() { this.name = ''; this.date = new Date(); this.maxLimit = 0; this.source = ['']; this.deliveryMethod = ['']; this.currency.mxn = 0; this.currency.php = 0; } } export default Company;
It looks like you're not instantiating the currency field in your constructor. Try by changing the
currency: Currency;
to
currency = new Currency();
It's probably working with your companiesList
because probably (I'm guessing here) your backend instantiate them for you. And when you instantiate the newCompany
which I assume you do by yourself it's not working cause of the missing new Currency()
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