Can access t in script but not script setup?

[HittiGubbi]

I have a basic Vue single file component with the following kind of a script element:

<script>
    export default {
        computed: {
            someProperty() {
                return this.$t("some.property");
            }
        }
    }
</script>

This works without problems: the value of someProperty correctly changes based on the current locale.

The problem is that I would prefer to use script setup instead, as that is what I am using everywhere else, but I have been unable to find information how to achieve that. E.g. the following two attempts result in error about t being undefined:

<script setup>
    import { computed } from 'vue';
    const someProperty = computed(() => this.$t.("some.property"));
</script>

<script setup>
    import { computed } from 'vue';
    const someProperty = computed(() => t.("some.property"));
</script>

So how can I access t inside a script setup element? I naturally want to do this in same manner as in the normal script, that is, without explicit import of t in different single file components.

[kazupon]

So how can I access t inside a script setup element? I naturally want to do this in same manner as in the normal script, that is, without explicit import of t in different single file components.

You need to use the useI18n in script setup.

<script setup>
    import { computed } from 'vue';
    import { useI18n } from 'vue-i18n';
    const { t } = useI18n();
    const someProperty = computed(() => t.("some.property"));
</script>

See the details composition API section:
https://vue-i18n.intlify.dev/guide/advanced/composition.html

[HittiGubbi]

Thanks, this works. So it seems that the explicit import cannot be avoided in script setup elements.

[CaiWenlie]

but how can i use i18n in js file?

[MarcMoerkeberg]

For some reason, I thought I had to use the custom instance of i18n I mounted on app in main.ts. The documentation however also specifies it should be done with useI18n() from the plugin library, I guess I was just stuck in my old ways of using i18n previously with Vue and TypeScript.
Thank you very much for the clear and concise answer @kazupon 😄

[realtebo]

"Not available in legacy mode"

[Carlozc90]

if you have the error "Not available in legacy mode"

const i18n = createI18n({
legacy: false,
...