I want to create an input field that the user can fill out. The catch is that I don't want them to fill this field in with special characters. Currently, I have this html setup:
<input class="rc-input-editing" id="bioInput" type="text" v-model="wrappedBioName">
And this Vue.js setup (As you can see, I'm trying to approach this problem using a computed setter) :
data () {
return {
newBioName: '',
}
},
computed: {
wrappedBioName: {
get () {
alert('getting new name!')
return this.newBioName
},
set: function (newValue) {
const restrictedChars = new RegExp('[.*\\W.*]')
if (!restrictedChars.test(newValue)) {
this.newBioName = newValue
}
}
}
Currently, my issue is that the client is able to continue filling out the text input field, even when this.newBioName isn't updating. In other words, they are able to enter special characters into the input field, even though the this.newBioName isn't being updated with these special characters.
This behavior is different than what I'm expecting, given my current understanding of v-model. Based on what I've read until now, v-model binds the input element to some vue instance data, and that vue instance data to the input element (two way binding). Therefore, I'm expecting that the text in the text input field will directly match the value of this.newBioName.
Clearly, I'm missing something, and would appreciate a second pair of eyes!
Vue.js two way binding system doesn't work as you expected. Each binding process works one way each time. So, the thing you should do is not to let the input text change.
Try keypress event instead of computed property like this:
<input class="rc-input-editing" id="bioInput" type="text" v-model="newBioName" #keypress="nameKeyPressAction">
data() {
return {
newBioName: ""
};
},
methods: {
nameKeyPressAction(event) {
const restrictedChars = new RegExp("[.*\\W.*]");
const newValue = this.newBioName + event.key;
if (!restrictedChars.test(newValue))
this.newBioName = newValue;
return event.preventDefault();
}
}
Edit:
When you set a data property or a computed property as v-model of an input, vue associates them and yet, if user updates dom object via the input, property's setter is triggered and the process ends here. On the other hand, when you change the value of the property on javascript side, vue updates the dom object and this process also ends here.
In your sample code, it seems like you expect that the computed property's getter to set the dom again but it can't. The property is already updated via dom change and it can't also update it. Othervise, there might occur infinite loop.
Related
I'm using bootstrap-vue table, according to documentation regarding formatter callback: https://bootstrap-vue.org/docs/components/table .
A variable is defined in data(), I will need this variable as a flag to control the cell content.
data() {
return {
aFlag: 0,
}
}
Then in the fields I use the formatter call back:
{ key: 'value', label: 'Value', formatter: this.updateValue},
In the methods area I use updateValue to update the flag:
methods: {
updateValue(value) {
..
aFlag = value
..
}
}
Then error "You may have an infinite update loop in a component render function." happened here.
If I want to do such a thing, is there any best practice? The cell content may cause other cell's change, so currently I use a variable to control the behavior as a flag. Thanks in adavance.
The formatter callback is only intended to change how the value is displayed to the user, not change its value.
If you want to be able to change the value, I'd suggest using a slot for the value property and use v-model on a form component within the slot:
<template v-slot:cell(value)="data">
<input type="text" v-model="data.value"/>
</template>
Per the docs you can add the attribute use-input to a QSelect component to introduce filtering and things of that nature: https://quasar.dev/vue-components/select#Native-attributes-with-use-input.
However, if you type something into one of these fields and click outside of it, the text gets removed.
Is there any way to grab that text in Vue before it gets removed and do something with it?
Since v1.9.9 there is also a #input-value event described in the q-select api.
As the api says it's emitted when the value in the text input changes. The new value is passed as parameter.
In the examples there's a filter function, so there you can save it in a data variable:
methods: {
filterFn (val, update, abort) {
update(() => {
this.myDataVariable = val;
})
}
}
I have problem understanding why THE SAME mutation fails to refresh data displayed in components (although it does change underlying vuex store data!) if it is called from one of the components, but it does refresh the data if called from another component?
I am updating Filter objects stored in store this way: state.report.filters[], where filters is array of Filter objects.
const state = {
report: {
filters: [], // array of Filter objects
...
}
}
My mutation looks for a filter in the array and substitutes the whole Filter object.
const mutations = {
setFilter: (state, newFilterValue) => {
let changedFilter = state.report.filters.find(filter => {
return filter.fieldName === newFilterValue.fieldName;
});
changedFilter = newFilterValue;
}
}
The mutation is called from a method of Filter class defined like this (separate module):
import { store } from './store';
export class Filter {
constructor ({
...
} = {}) {
this.operators = []; // Array of Operator objects
this.value = []; // Array of values - in this case Dates
};
updateOperator (operatorName) { // this mutation refreshes components when executed
this.operator[0] = new Operator(operatorName);
store.commit('setFilter', this); // whole object passed to the mutation
};
updateValue (newValue) { // this mutation changes store value, but fails to refresh components
this.value[0] = newValue; // newValue is a Date
store.commit('setFilter', this);
};
};
The app displays data in rows (each Filter has a separate row), each row contains cells, of which one contains components dedicated to Filter's value and Operator. These dedicated components receive as props callback functions which are methods of the Filter object. They execute the callback functions when a new value is entered passing the value to the Filter which then updates a relevant property and calls the mutation passing in both cases the whole Filter object as payload.
// TABLE CELL COMPONENT displaying filter value and operator
<template>
<td>
<operator-component
:iconName="proppedFilterObject.operator.iconName"
:callback="proppedFilterObject.updateOperator.bind(proppedFilterObject)"
></operator-component>
<value-component
:date="proppedFilterObject.value[0]"
:callback="proppedFilterObject.updateValue.bind(proppedFilterObject)"
></value-component>
</td>
</template>
<script>
export default {
props: ['proppedFilterObject'] // whole filter object
};
</script>
// OPERATOR COMPONENT
<template>
<div #click.stop="chooseOperator">
{{ iconName }} // some operator value display
</div>
</template>
<script>
export default {
methods: {
chooseOperator () {
const modal = new ChooseOperatorModal({
callback: this.callback // this displays another modal for receiving data. The modal calls the callback.
});
},
},
props: ['callback', 'iconName']
};
</script>
// VALUE COMPONENT
<template>
<date-picker v-model="computedDate"> // THIRD PARTY COMPONENT
</date-picker>
{{ date }} // additional display to verify if there's a problem within 'date-picker'
</template>
<script>
import DatePicker from 'vue2-datepicker'; // THIRD PARTY COMPONENT
export default {
components: { DatePicker },
computed: {
computedDate: {
get: function () {
return this.date;
},
set: function (newValue) {
this.callback(newValue);
}
}
},
props: ['callback', 'date']
};
</script>
So, if eg. I enter new operator value from Operator component, everything refreshes. When I enter a new value in the value component, the mutation is executed and store value changed, but displayed data are not refreshed. However, if afterwards I change an operator all the components will refresh and value will get displayed. Even if I change operator in a different Filter object(!). Ie:
a) Change in report.filters[0].value - display not refreshed, but...
b) then change report.filters[1].operator - both report.filters[1].operator AND PREVIOUSLY CHANGED report.filters[0].value get refreshed(?!).
What can be a reason of such behaviour? Where to look for the problem?
Some additional remarks:
1) I am using a third party component "vue2-date-picker" for date choice and display. However it does not seem to be responsible for the problem, as if I try to display the new value just in {{ }} notation it behaves the same way. I have used the date picker in other components and there it functions correctly as well.
2) In the code samples I left out most imports/exports and other seemingly irrelevant elements to keep the question reasonably short.
There are a lot of problems with the code and several of them are contributing to the problems you're seeing. A full, thorough answer that addresses all of these problems would be ridiculously long so instead I will skim through them without going into huge amounts of detail. You will need to do some further reading and experimentation to understand each of these topics properly.
Let's start with this line in the mutation:
changedFilter = newFilterValue;
This line assigns a new value to the local variable changedFilter. That's all. As it's the last line of the mutation the net result is that it doesn't really do anything.
Presumably your intent was to update the array state.report.filters, replacing the old entry with a new entry. However, just updating a local variable isn't going to do that.
At this point you may be wondering 'If that doesn't do anything, then why is the state in my store changing?'. I'll come to that in a moment but first let me prove to you that your existing code does nothing.
Try removing the code inside setFilter completely. Just leave an empty function. Then try clicking around in the UI just like you did before. You'll find that the store state updates just the same as it did before, even though you've removed the code to update the array.
The correct way to implement that mutation would be to use findIndex to find the relevant index and then use either Vue.set or the array's splice method to update the array accordingly. That will change the item in the array. However...
This brings us back to the earlier question. Why is the state updating if the mutation does nothing?
This is because you're using the same object in multiple places. The Filter object held in the array is the same object that your UI is editing. There are no copies being taken, there is just a single object. So when you change the properties of that object inside updateOperator or updateValue this will immediately be reflected inside the store. Calling the setFilter mutation is just asking the store to replace an object with itself.
There's nothing specific to Vue about this. This is just the standard behaviour of reference types in JavaScript. It is also common with many other programming languages that don't directly expose pointers. It can be useful to learn a little about how pointers work in other languages as it will give you a better initial mental model before attempting to understand how reference types behave in JavaScript. Understanding the difference between 'by value' and 'by reference' may also be a useful starting point.
The next topic to cover is reactivity, which very much is a Vue topic.
Specifically, there are certain changes that Vue can't detect. These are usually referred to as the reactivity caveats. You can find more about them in the official documentation:
https://v2.vuejs.org/v2/guide/reactivity.html#Change-Detection-Caveats
https://v2.vuejs.org/v2/guide/list.html#Caveats
There are at least two lines in your code that violate these rules:
this.operator[0] = new Operator(operatorName);
and
this.value[0] = newValue;
You can't set array entries directly by index. The array will update but it won't trigger any reactive dependencies within Vue. Instead you need to use either Vue.set or one of the array methods, e.g. push, pop, splice, etc.. In this example you could use splice.
e.g. Using Vue.set:
Vue.set(this.value, 0, newValue);
e.g. Using splice:
this.value.splice(0, 0, newValue);
Why does all of this matters?
Well Vue will only re-render a component if its reactive dependencies have changed. They are very similar to computed properties in that regard. Here's how it works...
Vue compiles the template down to a function. That function is referred to as the render function. When rendering a component Vue calls the render function and that function returns a description of how to render the component. Any reactive properties that are touched while that function is running will be recorded as dependencies. If, at some point in the future, the value of one of those reactive properties changes then Vue will rerun the render function to generate a new rendering of that component.
There are two key points to take out of this description:
If you fall foul of one of the reactivity caveats then Vue won't know the dependency has changed, so it won't re-render the component.
The render function runs as a whole. It doesn't just target a small chunk of the template, it always runs the whole thing.
So if you change a dependency in a non-reactive way (i.e. one of the caveats) it won't trigger a rendering update. But if you subsequently update a dependency properly, Vue will detect that and will rerun the render function. When it runs it will run the whole thing, so any new values will be picked up, even if they weren't detected when they changed.
It isn't immediately clear to me which rendering dependency is causing your component to re-render. However, it only needs one of them to change in a detectable manner. Any other changes will then get pulled in incidentally when the render function runs and reads their current values.
That covers why your code isn't working. However, I would also worry about your decision to introduce a Filter class. I understand how that may be appealing if you've come from some other OO environment but it isn't typically how Vue is used. It is possible to make it work but you will need a good understanding of both JavaScript reference types and the Vue reactivity system to avoid falling through the cracks. There is no reason why using a specific class to hold your data can't be made to work but in practice it usually ends up being less maintainable than not using such a class. A more typical Vue approach would be to use simple, anonymous objects/arrays to hold the data and then for the data owner (either a component or store module) to be responsible for making any mutations to that data. Events are used to pass changes up the component hierarchy rather than callback props.
Ultimately you will need to judge whether the Filter class is justified but it is probably not what future maintainers of your code will be expecting.
I have two components in mu app.vue and i will send data from app.vue to my first component(filter component) at the time of page load.
Now based on the user actions in the displayed data in the second component i need to pass new vales back to the first component.
There i am using a and a . Consider one of the props i receive in the first component is "nselectedOption" and i do this in data: { return { selectedOption: this.nselectedOption }} to avoid mutation warning.
Now everytime i update the values for this component from second component, i am seeing changes in "nselectedOption" only and not in "selectedOption". Can you explain why is that ?
I need the updated value into a v-model of .
1. If i use "nselectedOption" it is updating the textbox but while editing the value throws error.
2. If i use "selectedOption" it is not updating the values in the textbox itself.
I have even tried using the computed values to return the value, it works but if i try to change values in other options in the filter component the already updated values displays null or nothing.
Please help me. Is this problem can be solved using State Management Concept or do i have to have a separate compoenent other than App.Vue to do all this so that it would act as a parent/child kinda thing or is there anyother way to overcome this.
Try using watcher. If you watch for nselectedOption, everytime it changes, the watcher will fire and bind the changed value to selectedOption.
props: ['nselectedOption'],
data: {
selectedOption
},
watch: {
nselectedOption: function (val) {
this.selectedOption = val
}
}
Also, if the prop you are watching is an object/array, consider using spread operator if you want to make a local copy to avoid mutation.
this.someObj = { ...someProp }
Suppose that I have an input element bound like this:
<input :value="somedata">
The user types something in the input, and since I am not using v-model or altering somedata through a handler, the value of the element is now different from somedata. This is what I want, but I would also like to have the following capability:
Without changing the value of somedata I would like to be able to notify the element so that it sets its value equal to somedata again. Something like knockout's notifySubscribers() or valueHasMutated()
Is that possible in vue.js?
UPDATE: A clear illustration of the issue here: https://jsfiddle.net/gtezer5c/3/
It's a little difficult interpreting what exactly the requirements and acceptance criteria might be to suit your needs, and I thought Bill's solution was what you were after, but after all the updates and clarifications, I think I understand a little more what you're trying to accomplish: in short, I think you need a generic way to have an input that can hold a value but that can be independently reverted to some other value.
Please have a look at this CodePen. I believe it's providing what you're trying to do. It allows you to create an input element as a revertable component, which can optionally be passed a default value. Any changes to that input are maintained by the component with its value data property. It will not be observing/pulling in any lastKnownGood type of value because any reversion will be pushed into the component from outside.
Externally to the revertable component, you can $emit a revert event with a new value that will cause either all revertable components or a single revertable component (with a matching ID) to be reverted.
I feel like it's mostly a clean solution (assuming I'm understanding the requirements correctly), except that in VueJS 2 we have to use a standalone, shared Vue object to pass the events when there is no parent-child relationship. So you'll see:
const revertBus = new Vue()
defined in global scope in the demo. And the revertable component will use it to receive incoming messages like so:
revertBus.$on('revert', (value, id) => { ... }
and the controlling Vue object that is triggering the messages will use it like this:
revertBus.$emit('revert', this.reversionValue, targetId)
You can also emit the event with a null value to cause the revertable component to reset its value to its initial default value:
revertBus.$emit('revert', null, targetId)
Again, it's a mostly clean solution, and though it might not fit perfectly inline with what you're trying to accomplish, I'm hoping it might at least help you get closer.
I'm not sure I'm following properly but I'll give it a shot.
What I think you want is to only update some values when their "temporary" values meet some type of condition. Here's how I was thinking of it.
<div id="app">
<input v-model="tempValues.one">
<input v-model="tempValues.two">
<input v-model="tempValues.three">
<pre>{{ values }}</pre>
<pre>{{ tempValues }}</pre>
</div>
Then, in my component, I watch tempValues and only update values when a condition is met.
new Vue({
el: '#app',
data: {
values: {
one: '',
two: '',
three: '',
},
tempValues: {},
},
created () {
// Create the tempValues based on the real values...
this.tempValues = Object.assign({}, this.values)
},
methods: {
updateValues (tempValues) {
// Only updating the values if all the tempValues are longer than 3 characters...
var noneEmpty = Object.values(tempValues).every((value) => value.length > 3)
if (noneEmpty) {
this.values = Object.assign({}, tempValues)
}
},
},
watch: {
// Watch tempValues deeply...
tempValues: {
handler (tempValues) {
this.updateValues(tempValues)
},
deep: true,
},
},
})
Here's a quick demo: https://jsfiddle.net/crswll/ja50tenf/
yourvar.__ob__.dep.notify()
works on objects and arrays
Yes, You should be able to do this with help of v-on:input. You can call a function on input and put your logic of checking and updating in this function:
<input :value="somedata" v-on:input="yourMethod">
In fact if you look at the documentation, <input v-model="something"> is syntactic sugar on:
<input v-bind:value="something" v-on:input="something = $event.target.value">
so instead of assigning variable something to value inputted, you can put your logic in that place.