Vue 3 Type 'string' is not assignable to type 'Ref<string>'

I have this code which works perfectly fine on my localhost. But Typescript throws me an error Type ‘string’ is not assignable to type Ref<string>.

let placeholderTitle = ref<string>('')


function beforeDragStart() {
    placeholderTitle = ''
    ....
}

Can somedy tell me please what is the problem with this code.

Secondly why this composition api allowes me to asign value straight to the placeholderTitle and placeholdertitle.value = throws me an error?

>Solution :

Being a Ref, placeholderTitle has to be a constant (const instead of let).

Using let allows you to change the content of placeholderTitle, but then Typescript throws legitimately a type error Type 'string' is not assignable to type Ref<string>.

To change the content of a Ref, you have to change its inner .value:

function beforeDragStart() {
    placeholderTitle.value = ''
    ....
}