vuejs use data from parent, but parent data usually update - vue.js

Question

there are two .vue file and one is parent and another is child.
I am developing 'Sending file' function with Modal.
I will upload file data in parent.vue.
and when I click 'Send', child.vue will be popped up!
and I will choose, target who receive this file data.
and finally, I click 'Send' button, get connection to Backend server.
This is parent.vue
<<templete>>
<script>
export default {
name: 'BillingView',
components: {
EmailSender
},
data() {
return {
uploaded_file: '',
file_data: {},
is_uploaded: false,
popupVal: false
}
},
methods: {
sendEmail() {
if (this.is_uploaded == false) {
alert('Upload your file');
} else {
<< parsing file data>>
this.file_data = JSON.parse(JSON.stringify(this.parsed_uploaded_file));
this.popupVal = (this.popupVal) ? false : true
}
},
popupClose: function ( value ) {
this.popupVal = value
}
}
}
</script>
This is child.vue
<<templete>>
<script>
import axios from 'axios';
export default {
name: 'EmailSender',
props: {
popupVal: Boolean,
file_data: {
type: Object,
default: () => {
return {}
}
}
},
data: () => ({
}),
computed: {
popUp: {
get() {
return this.popupVal
},
}
},
created() {
},
methods: {
sendEmail() {
let req_data = {};
req_data ['file'] = file_data;
axios.post(process.env.VUE_APP_BASE_API + 'email/',
{
req_data ,
headers: {
'Content-Type': 'application/json;charset=UTF-8-sig'
}
}
).then(res => {
console.log('SEND EMAIL SUCCESS!!');
console.log('SEND EMAIL RESPONSE::', res, typeof (res));
})
.catch(function () {
console.log('SEND EMAIL FAILURE!!');
});
}
}
};
</script>
but here, "req_data ['file'] = file_data;" the file_data is empty, {}.
I expect when I update file_data in parent vue, child can know and use updated file data.
how can I do?

Answer 1

You have to make sure you send file_data as a prop to your component. e.g. Your component is 'myPopup' and you should use it as below to send file_data as a prop:
<myPopup :myData="file_data" >
In this case, you can get file_data as 'myData' in the child component as below
After changes, your props should be:
props: {
myData: {
type: Object,
default: () => {
return {}
}
}
},
Your function should be:
Also, don't forget to use 'this' keyword. this.myData instead of myData in function.
methods: {
sendEmail() {
let req_data = {};
req_data['file'] = this.myData;
// axios here
};
},