Vue Basic Components 'T' has not been declared

After updating to Vue 3.4.30, I encountered an issue while trying to use Generic components. When attempting to use T as a type for a property, I received an error message. Any guidance or suggestions on how to resolve this would be greatly appreciated.

I previously used an older version of Vue and have not updated any other packages, as indicated in the package.json excerpt provided below:

"vue": "^3.2.37"

https://i.sstatic.net/Hlu4Do5O.png

            "dependencies": {
        "@codemirror/lang-json": "^6.0.1",
        "@codemirror/lint": "^6.4.2",
        "@date-io/date-fns": "^2.17.0",
        ... (omitted for brevity)
    },
    "devDependencies": {
        "@quasar/vite-plugin": "^1.5.0",
        "@types/jest": "^28.1.8",
        ... (omitted for brevity)
    }
}

What I've tried so far:

<script setup lang="ts" generic="T">

<script setup lang="ts" generic="T extends ChildEntryModel">
typescriptvuejs3

Answer №1

This code will not function properly because when you define props using the default defineProps({...}) macro, it utilizes actual JavaScript values for the prop definitions. Since T is just a type and does not translate into a real JavaScript object, it remains undefined during the runtime of defineProps.

According to the documentation at https://vuejs.org/guide/components/props.html, you can specify your component props using pure type annotations like this:

defineProps<{ modelValue: T}>()

In your component, you can use the generic type parameter T like this:

Vue SFC Playground example

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