Navigating the flow of data between the view and model in Angular can be a complex task

Question

Navigating the flow of data between the view and model in Angular can be a complex task

After using Angular (version 5.2) for a few months, I've come across a situation where I feel like I might be overlooking an obvious solution. The issue I'm facing involves manipulating data between the view and the model.

For instance, in my project where I am working on a simplified app that interacts with Microsoft Project, users are supposed to input start and end dates for each task. Based on certain conditions within my component, these dates may need to be adjusted directly or affect another variable in the task. Therefore, using something like

<input type="date" [(task.startDate)] />

doesn't seem ideal. My workaround for this has been utilizing code like

<input type="date" (change)="processTheDate($event.value, task)" [value]="task.startDate" >

private processTheDate(value: Date, task: Task){

     //do some processing

     //set the value
     task.startDate = value;
}

However, according to some discussions I've read online, this might not be the best approach (source).

My question is two-fold:

1. What are the drawbacks of bypassing Angular's data binding in the manner shown above?

2. Can you suggest a more effective alternative?

angular typescript

Answer 1

Answer №1

There is no inherent issue with the code, except for calling a private method from the view. Typically, forms are used to collect information and take action upon submission. Therefore, binding form controls to a model simplifies this process.
Other options include:
- You can opt for a template-based form like ngModel. In addition to binding the field to task.startDate, you can use (ngModelChange) to respond to changes in the model and handle date processing. Alternatively, you may utilize a setter instead of a public field to perform actions within the setter function.
- Another approach is to use a reactive form and subscribe to the valueChanges observable of the FormControl. This will notify you whenever the value changes, allowing you to process the date accordingly.

Answer 2

There is no inherent issue with the code, except for calling a private method from the view. Typically, forms are used to collect information and take action upon submission. Therefore, binding form controls to a model simplifies this process.
Other options include:
- You can opt for a template-based form like ngModel. In addition to binding the field to task.startDate, you can use (ngModelChange) to respond to changes in the model and handle date processing. Alternatively, you may utilize a setter instead of a public field to perform actions within the setter function.
- Another approach is to use a reactive form and subscribe to the valueChanges observable of the FormControl. This will notify you whenever the value changes, allowing you to process the date accordingly.

Answer 3

Answer №2

Your solution looks solid to me.

In my opinion, utilizing ngModel is typically preferred for two-way binding since it eliminates the need to write code that synchronizes values repeatedly. However, if extensive logic needs to be executed when the value changes, using change is totally acceptable.

You can also combine both approaches if you require two-way binding alongside certain logic upon value modification.

<input type="date" (change)="onStartDateChange($event.value, task)" 
       [(ngModel)]="task.startDate">

onStartDateChange(value: Date, task: Task){

     //perform some operations

     //assign the value
     task.startDate = value;
}

Answer 4

Your solution looks solid to me.

In my opinion, utilizing ngModel is typically preferred for two-way binding since it eliminates the need to write code that synchronizes values repeatedly. However, if extensive logic needs to be executed when the value changes, using change is totally acceptable.

You can also combine both approaches if you require two-way binding alongside certain logic upon value modification.

<input type="date" (change)="onStartDateChange($event.value, task)" 
       [(ngModel)]="task.startDate">

onStartDateChange(value: Date, task: Task){

     //perform some operations

     //assign the value
     task.startDate = value;
}

Navigating the flow of data between the view and model in Angular can be a complex task

Answer №1

Answer №2

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