Let's talk about the problem that the radio cannot be changed in uniapp data echo

Recently, in the process of developing a uniapp project, I encountered a more difficult problem, which is the problem that the radio of data echo cannot be changed.

First of all, we need to understand the basic use and working principles of uniapp and radio.

uniapp is a cross-platform mobile application development framework. It can generate multiple mobile applications for iOS, Android and so on at the same time, making it convenient for developers to develop cross-platform applications. Radio is a form control that allows the user to select one of multiple options. In vue, we can use v-model to control the selected state of the radio.

In uniapp, we usually use data binding to control the selected state of the radio. For example, we can store the selected value of radio by defining a variable in data, and then control the selected state of radio through v-model binding, as shown below:

<radio-group v-model="radioValue">
  <radio :value="&#39;value1&#39;">选项1</radio>
  <radio :value="&#39;value2&#39;">选项2</radio>
  <radio :value="&#39;value3&#39;">选项3</radio>
</radio-group>

Among them, radio-group is used Wrap multiple radio controls, v-model is used to bind the selected value, and value is used to specify the value of each radio control.

However, when we need to echo the saved data to the radio control on the editing page, we need to assign a value to the radio control. At this time, we usually perform data echo operations in the created life cycle function, as shown below:

created() {
  this.radioValue = 'value1'; // 假设已经保存的值为value1
}

Here, we set the value of radioValue to the saved value value1 to implement the echo operation . However, when we tried to change the selected status of the radio, we found that it had no effect.

This is because in uniapp, the v-model binding of the radio control can only achieve two-way data binding, but not one-way data binding. In other words, the assignment operation we performed in the created life cycle function was only assigned locally and was not synchronized to the radio control, so when we change the selected state of the radio, it will not be updated to the data. .

The solution to this problem can be achieved by using the ref attribute and $refs attribute provided by uniapp. Ref can be used to register reference information for elements or subcomponents, and the registered reference information can be accessed through $refs. We can set the ref attribute of the radio control to radioRef, and then set the checked attribute of radioRef to true in the created life cycle function to realize the function of data echo and selected status synchronization.

The sample code is as follows:

<radio-group ref="radioGroup">
  <radio ref="radio1" value="value1">选项1</radio>
  <radio ref="radio2" value="value2">选项2</radio>
  <radio ref="radio3" value="value3">选项3</radio>
</radio-group>

created() {
  this.$nextTick(() => { // 使用$nextTick函数，等待页面渲染后再进行操作
    const radioGroup = this.$refs.radioGroup;
    const radio1 = this.$refs.radio1;
    const radio2 = this.$refs.radio2;
    const radio3 = this.$refs.radio3;
    const value = 'value1'; // 假设已经保存的值为value1
    if (value === radio1.value) {
      radio1.checked = true;
      radioGroup.$emit('change', 'value1'); // 通过$emit触发radio-group的change事件，将选中的值同步到data中
    } else if (value === radio2.value) {
      radio2.checked = true;
      radioGroup.$emit('change', 'value2');
    } else if (value === radio3.value) {
      radio3.checked = true;
      radioGroup.$emit('change', 'value3');
    }
  });
}

Here, we use $refs to get instances of radio-group and each radio control, and then set the selected state based on the saved value value, And trigger the change event of the radio-group through the $emit function, and synchronize the selected value to the data.

To sum up, by using $refs and $emit to realize the function of radio data echo and selected status synchronization, the problem that the data echo radio cannot be changed in uniapp can be solved.

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