v-for and v-if not working together in vue.js

问题

A form is used to submit text and two options which tell vue which column to display the text in. When the col2 radio button is checked the submitted text should display in column 2. This is not happening, on column 1 text is displaying.

I have two radio buttons which should pass the value 'one' or 'two' to a newInfo.option On submnit a method pushed the form data to the array 'info'.

<input type="radio" id="col1" value="one" v-model="newInfo.col">
<input type="radio" id="col2" value="two" v-model="newInfo.col">

This data is being pushed to the array 'info' correctly and I can iterate through it. I know this is working because I can iterate through the array, an console.log all the data in it. All the submitted form data is there.

Next I iterate through this array twice in the template. Once for info.col==="one" and the other iteration should only display when info.col==="two". I am using a v-for and v-if together, which the vue.js documentation says is ok to do,

https://vuejs.org/v2/guide/conditional.html#v-if-with-v-for

<div class="row">
            <div class="col-md-6">
                <ol>
                    <li v-for="item in info" v-if="item.col==='one'">
                        text: {{ item.text }}, col: {{ item.col }}
                    </li>
                </ol>
            </div>
            <div class="col-md-6">
                <ol>
                    <li v-for="item in info" v-if="!item.col==='two'">
                        text: {{ item.text }}, col: {{ item.col }}
                    </li>
                </ol>
            </div>
        </div>

The full vue.js code is on github here

And it is running on gh-pages here

回答1:

Remove ! from second if v-if="item.col==='two'"

better you can do this way (to iterate only once):

<div class="row" v-for="item in info">
            <div class="col-md-6">
                <ol>
                    <li v-if="item.col==='one'">
                        text: {{ item.text }}, col: {{ item.col }}
                    </li>
                </ol>
            </div>
            <div class="col-md-6">
                <ol>
                    <li v-if="item.col==='two'">
                        text: {{ item.text }}, col: {{ item.col }}
                    </li>
                </ol>
            </div>
        </div>

回答2:

Why don't use the power of Computed Properties ?

computed: {
  infoOne: function () {
    return this.info.filter(i => i.col === 'one')
  },
  infoTwo: function () {
    return this.info.filter(i => i.col === 'two')
  }
}

Then on each list just iterate over its respective property without the need to check. Example

<ol>
   <li v-for="item in infoOne">{{item}}</li>
</ol>

Here the working fiddle

回答3:

Your second check is !item.col==='two' and would only display if it does not equal 'two'.

EDIT: The ! not operator is likely binding more closely than === so that will always return false. Add brackets to control the order of application. I say likely because it may be a bit of Vue magic that I'm not familar with, rather than a pure JavaScript expression.

I think you want to remove that exclamation mark. Or to make it !(item.col==='one') to display for any value other than 'one'.

回答4:

It's not recommended to use v-if and v-for on the same element!

来源：https://stackoverflow.com/questions/48933606/v-for-and-v-if-not-working-together-in-vue-js

标签

Vue.js

radio-button

v-for