Encountered a TypeScript error in Vue 3 when attempting to access state within the setup method: "TS error -

Question

Encountered a TypeScript error in Vue 3 when attempting to access state within the setup method: "TS error -

Currently, I am working with Vue 3 and TypeScript. In the Setup function, I have defined some states like this:

export default defineComponent({
  setup() {
    const isLoadingSendData = ref(false)

    return { isLoadingSendData }
  
  },
  methods: {
    disableBtn(): boolean {
       // When using Webstorm, I encountered an error: TS2339: Property 'isLoadingSendData' doesn't exist 
       // on type 'disableBtn(): boolean'
       if(this.isLoadingSendData) {
         return // do something
       }
       return // do something
    }

  }
})

This is just one example of a particular scenario. The red error under this.isLoadingSendData in my IDE is confusing me. Can anyone provide insights on why this error occurs?

typescript vue.js vuejs3

Answer 1

Answer №1

When using the composition API, you cannot directly access variables declared in the setup() function within options like methods and data. If you need to define a method within the composition API, the structure should be as follows:

export default defineComponent({
  setup() {
    const isLoadingSendData = ref(false);
    const disableBtn = (): boolean => {
      if (isLoadingSendData.value) {
        return; // do something
      }
      return; // do something
    };

    return { isLoadingSendData, disableBtn };
  }
});

If you prefer to use the options API instead, you can define it like this:

export default defineComponent({
  data() {
    return {
      isLoadingSendData: false
    };
  },
  methods: {
    disableBtn(): boolean {
      if (this.isLoadingSendData) {
        return; // do something
      }
      return; // do something
    }
  }
});

Therefore, the decision lies between using the composition API or the options API.

Another syntax option for the composition API is to use the <script setup> tag. Here is an example:

<script setup lang="ts">
import { ref } from "vue";

const isLoadingSendData = ref(false);
const disableBtn = (): boolean => {
  if (isLoadingSendData.value) {
    return; // do something
  }
  return; // do something
};
</script>

You can access everything declared within the <script setup> tag in the template section.

Answer 2

When using the composition API, you cannot directly access variables declared in the setup() function within options like methods and data. If you need to define a method within the composition API, the structure should be as follows:

export default defineComponent({
  setup() {
    const isLoadingSendData = ref(false);
    const disableBtn = (): boolean => {
      if (isLoadingSendData.value) {
        return; // do something
      }
      return; // do something
    };

    return { isLoadingSendData, disableBtn };
  }
});

If you prefer to use the options API instead, you can define it like this:

export default defineComponent({
  data() {
    return {
      isLoadingSendData: false
    };
  },
  methods: {
    disableBtn(): boolean {
      if (this.isLoadingSendData) {
        return; // do something
      }
      return; // do something
    }
  }
});

Therefore, the decision lies between using the composition API or the options API.

Another syntax option for the composition API is to use the <script setup> tag. Here is an example:

<script setup lang="ts">
import { ref } from "vue";

const isLoadingSendData = ref(false);
const disableBtn = (): boolean => {
  if (isLoadingSendData.value) {
    return; // do something
  }
  return; // do something
};
</script>

You can access everything declared within the <script setup> tag in the template section.

Answer 3

Answer №2

When utilizing Vue 3 with the setup function, there is no need to utilize the methods function as seen in Vue 2 and previous versions. Everything can be referenced directly in the template from the return object within the setup function. It's also important to wrap the script section with lang="ts" for TypeScript support.

<script lang="ts">
export default defineComponent({
  setup() {
    const isDataLoading = ref(false)

    return { isLoadingSendData }
  }
})
</script>

<template>
  <div v-if="isDataLoading">
    <p>Loading...</p>
  </div>
  <div v-else>
    <p>Finished Loading</p>
  </div>
</template>

Answer 4

When utilizing Vue 3 with the setup function, there is no need to utilize the methods function as seen in Vue 2 and previous versions. Everything can be referenced directly in the template from the return object within the setup function. It's also important to wrap the script section with lang="ts" for TypeScript support.

<script lang="ts">
export default defineComponent({
  setup() {
    const isDataLoading = ref(false)

    return { isLoadingSendData }
  }
})
</script>

<template>
  <div v-if="isDataLoading">
    <p>Loading...</p>
  </div>
  <div v-else>
    <p>Finished Loading</p>
  </div>
</template>

Answer 5

Answer №3

Adding additional information to the existing answers, Vue3 offers a simpler option called setup script. I suggest using the Volar extension over Vetur for the most up-to-date Vue setup syntax

<script setup lang="ts">
import { ref, Ref, computed, ComputedRef } from "vue";

const isLoadingSendData: Ref<boolean> = ref(false);
//The `ref` above can be used in the template directly,
//or you can create a computed value if needed
const disableBtn: ComputedRef<boolean> = computed((): boolean => {
  return !isLoadingSendData.value
})
</script>

<template>
   <div>
      <button v-show="disableBtn">disabled button</button>
      <button v-show="!disableBtn">normal button</button>
   </div>
</template>

No need to explicitly return values as the setup script automatically provides them to the template. Rather than creating a function or computed property to check loading status, using the ref directly is recommended :)

Answer 6

Adding additional information to the existing answers, Vue3 offers a simpler option called setup script. I suggest using the Volar extension over Vetur for the most up-to-date Vue setup syntax

<script setup lang="ts">
import { ref, Ref, computed, ComputedRef } from "vue";

const isLoadingSendData: Ref<boolean> = ref(false);
//The `ref` above can be used in the template directly,
//or you can create a computed value if needed
const disableBtn: ComputedRef<boolean> = computed((): boolean => {
  return !isLoadingSendData.value
})
</script>

<template>
   <div>
      <button v-show="disableBtn">disabled button</button>
      <button v-show="!disableBtn">normal button</button>
   </div>
</template>

No need to explicitly return values as the setup script automatically provides them to the template. Rather than creating a function or computed property to check loading status, using the ref directly is recommended :)

Encountered a TypeScript error in Vue 3 when attempting to access state within the setup method: "TS error -

Answer №1

Answer №2

Answer №3

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