When using Vue to bind a data URI to the img src property, I noticed that the image in the browser only updates when there is

Currently, I am working on generating a base64 string to represent an image and passing that image data to a child component as part of an object property.

The object class I am using for this purpose has an image property along with some other properties. Interestingly, when the parent component updates either otherData or id, everything works smoothly and I see the changes reflected in the child component. However, whenever the image property is updated, the new image does not show up until I make a change to a different property within MyDataModel instance. For instance, modifying otherData triggers the display of the updated image on screen. This makes me wonder if the size of the image encoded in base64 (320x240 and around 150KB) might be causing Vue's change detection mechanism to struggle.

export default class MyDataModel {
    public id!: string;
    public image!: string;
    public otherData: string;

    constructor(init?: Partial<MyDataModel>) {
        Object.assign(this, init);
    }
}

In the parent component, I define a new object to hold the data for the child component:

private childData = new MyDataModel();

This is how I create the image in the parent component:

const data = this.$refs.cameraCanvas.toDataURL('image/png');
this.capturedImageData = data;

Subsequently, I assign the capturedImageData to the image property:

this.childData.image = this.capturedImageData;

The childData is then passed as a property to the child component:

<ChildComponent :data="childData"></ChildComponent>

Here's how the data property is declared in the child component:

@Prop({required: true}) private data!: MyDataModel // MyDataModel is a typscript class with an image property

Finally, this is how I attempt to display the image:

<b-img id="input-image" :src="data.image"></b-img>

Answer №1

Oh no, the familiar scenario of a child component not re-rendering upon update... my eternal rival 😏. When faced with this issue, the solution is to take action and essentially force (or rather coerce/trigger) a re-render of the child component during the update process. Here's a straightforward (and very vue-friendly) method to achieve this:

Begin by adding a new property to the data section of your parent component

/* ==== Parent component - script === */
data(){
  return {
  // ... other properties go here 
  componentKey: 0, // you can name this property anything you like, just ensure it's a number
  }
}

Next, connect this property to the child component

/* ==== Parent component - template === */
<ChildComponent :data="childData" :key="componentKey"></ChildComponent>

Subsequently, after setting the capturedImageData, modify the value of this property

this.childData.image = this.capturedImageData;
this.componentKey += 1;

This sequence should prompt a re-render of the child component, displaying the updated image.

Additionally, remember that you can also utilize this technique in response to emitted events from the child component to trigger a self-re-render as follows

<ChildComponent :data="childData" :key="componentKey" @someEmitEvent="componentKey += 1"></ChildComponent>

It may be a bit unconventional, but rest assured that it gets the job done.

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