What should I do if 'TypeError: Cannot set property 'xxx' of undefined' appears when using vue-resource in a Vue application?

With the popularity of the Vue.js framework, more developers are using third-party libraries in Vue applications to handle network requests. Among them, vue-resource is a plug-in based on Vue.js, which provides a way to communicate with the API through HTTP requests. But sometimes when using vue-resource to make network requests, you will encounter the problem of "TypeError: Cannot set property 'xxx' of undefined". So what causes this problem? How do we solve this problem?

Cause of the problem

When we use vue-resource to send network requests, we usually use the $http object to send the request in the Vue component, such as:

this.$http.get('/api/data')

Here, The $http object represents an instance of vue-resource, and the get() method is used to send HTTP GET requests and receive response data.

When the "TypeError: Cannot set property 'xxx' of undefined" error occurs, it is usually because the program is trying to set properties to an object of undefined type. When using vue-resource, this may be caused by the following reasons:

• The vue-resource plugin is not imported correctly in the Vue component.

Before using vue-resource, you need to import the vue-resource plug-in in the Vue component. It is usually imported globally in main.js, as shown below:

import Vue from 'vue'
import VueResource from 'vue-resource'

Vue.use(VueResource)

Note that Vue.use() must be used in front of the Vue instance to register vue-resource, otherwise it cannot be used correctly.

• The properties of the vue-resource instance are not set correctly.

When we use a vue-resource instance, we can define some default attributes to set the request URL, default request headers and request bodies, etc. These properties are usually set in main.js, as shown below:

Vue.http.options.root = 'https://api.example.com'
Vue.http.headers.common['Authorization'] = 'Bearer ' + token

If these properties are not set correctly, the vue-resource instance may not handle the request correctly.

• The vue-resource instance is not correctly accessed in the Vue component.

When we use the vue-resource instance in a Vue component, we need to access it correctly (usually call it this.$http object). Failure to access it correctly will result in a "TypeError: Cannot set property 'xxx' of undefined" error.

Solution

If you encounter the "TypeError: Cannot set property 'xxx' of undefined" error when using vue-resource, you can try the following solution:

• Confirm that the vue-resource plug-in has been imported correctly

Before using vue-resource in the Vue component, you need to ensure that the vue-resource plug-in has been imported correctly. You can check whether the main.js file is imported correctly and register the vue-resource plug-in using the Vue.use() method.

• Confirm that the vue-resource instance has been correctly configured

Define the default properties of the vue-resource instance in main.js, such as request URL and request headers. This ensures that the instance can handle requests correctly. For example:

Vue.http.options.root = 'https://api.example.com'
Vue.http.headers.common['Authorization'] = 'Bearer ' + token

• Confirm that the vue-resource instance is correctly accessed in the Vue component

When using vue-resource in the Vue component, you need to correctly access the vue-resource instance, usually Is using this.$http object. Before using this object, you need to make sure that the Vue.js framework is properly embedded, otherwise it will not work properly.

• Check the code logic

If none of the above methods can solve the problem, it may be a code logic problem. You can inspect the code to see where it needs to be fixed or optimized.

Summary

When using vue-resource to make network requests in a Vue application, when the "TypeError: Cannot set property 'xxx' of undefined" error occurs, it is usually because the vue-resource instance is not It is caused by incorrect configuration or Vue component not correctly accessing the vue-resource instance. In order to solve this problem, we need to confirm the correct import of the vue-resource plug-in, the correct configuration of the vue-resource instance, and correctly access the vue-resource instance in the Vue component. If the above method does not work, you can check the code logic to find out where optimization and repair are needed.

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