Two way binding react что это
Two-way Binding Helpers
Importing
LinkedStateMixin is an easy way to express two-way binding with React.
In React, data flows one way: from owner to child. We think that this makes your app’s code easier to understand. You can think of it as “one-way data binding.”
However, there are lots of applications that require you to read some data and flow it back into your program. For example, when developing forms, you’ll often want to update some React state when you receive user input. Or perhaps you want to perform layout in JavaScript and react to changes in some DOM element size.
In React, you would implement this by listening to a “change” event, read from your data source (usually the DOM) and call setState() on one of your components. “Closing the data flow loop” explicitly leads to more understandable and easier-to-maintain programs. See our forms documentation for more information.
LinkedStateMixin is just a thin wrapper and convention around the onChange / setState() pattern. It doesn’t fundamentally change how data flows in your React application.
LinkedStateMixin: Before and After
Here’s a simple form example without using LinkedStateMixin :
This works really well and it’s very clear how data is flowing, however, with a lot of form fields it could get a bit verbose. Let’s use LinkedStateMixin to save us some typing:
valueLink objects can be passed up and down the tree as props, so it’s easy (and explicit) to set up two-way binding between a component deep in the hierarchy and state that lives higher in the hierarchy.
Note that checkboxes have a special behavior regarding their value attribute, which is the value that will be sent on form submit if the checkbox is checked (defaults to on ). The value attribute is not updated when the checkbox is checked or unchecked. For checkboxes, you should use checkedLink instead of valueLink :
There are two sides to LinkedStateMixin : the place where you create the valueLink instance and the place where you use it. To prove how simple LinkedStateMixin is, let’s rewrite each side separately to be more explicit.
Understanding Data-binding in React and Angular
Understanding Data-binding in React and Angular
Data binding is an integral part of modern applications that get developed these days. Many frameworks and tools incorporate the data-binding technique to develop faster and easily debuggable applications. As a JavaScript developer, it is important to understand how this technique gets implemented in various JS frameworks and libraries. In this particular article, we are going to cover how this technique gets implemented in Angular and React. So what is data-binding?
The definition from Wikipedia states:
Data-binding is a technique that binds data sources from the provider and consumer together and synchronizes them.
The definition from Wikipedia is self-explanatory. But, let’s try and understand what data-binding means to React and Angular. Consider the following diagram:
How “Data Binding” Works
Both React and Angular use components to render User interfaces. The point to remember while using React or Angular is that the component’s logic contains all the data related to a component that gets displayed in the view(UI). The connection between the component’s logic and the data it displays is called data-binding. Data-binding is of two types:
One-way data binding
As the name suggests, the data in this particular connection is bound one-way. One-way data-binding implies that only one of the following connections can be applied:
According to one-way data-binding, we can apply only one of the following connections:
One Way Data Binding
Two-way data-binding
I think two-way data-binding now looks pretty straight forward. In two-way data-binding, the following connections are made at once:
Illustration of two-way data-binding:
Two Way Data Binding
As we can see in the above illustration, both connections are made at once i.e any change in view reflects in the component’s logic and any change in component’s logic reflects in the view. Now that we have discussed what data-binding actually means. Let’s understand how it works in React and Angular,
Data-binding in React
React was never really designed for two-way binding although two-way data-binding can be implemented in React. By default, the connection between a component and a view is always one-way bound. We can apply additional logic to a component so that the connection is made two-way. Let’s understand both bindings in react,
One-way data-binding in React
Like we stated before, one-way binding should perform one of the connections (View to Component or Component to View). In the case of React, we can only perform components to view connection. This means in React, by default there is no way that a view can change the component’s logic. Only the component’s logic can affect the view.
Component to View:
Example of Component to View binding in React
In the code above, we have built a component which displays a heading and a paragraph. Both these values are stored as state variables. The values of these variables are attached (bound) to the h3 and p elements respectively. As one can observe, any change in the value of the state variables is directly reflecting inside the view. By attaching the values of the state variables directly to the elements, we are implementing one-way data-binding in React.
View to Component:
Wait!! We just discussed above that React does not allow us to change the component’s logic from view. But, there’s a gotcha! React does not allow the view to change or update the component’s logic directly but, we can add event handlers to the view elements and change the component’s data. Let’s understand that with an example:
Consider the following component which allows us to change the model (Component) from the view:
Gaperton’s blog
Руководство по two-way data binding в React.
Во-первых, он таки в React есть. Называется value link. Это такой дизайн паттерн. И не смотря на то, что Фейсбук убирает свою кривую реализацию оного из React, он не может вам запретить его использовать.
Понимаем, что это такое, и учимся делать формы на React просто и приятно.
Во-вторых, этот паттерн способен на куда большее, чем примитивная его реализация в React. Например, он помогает весьма изящно делать валидацию ввода в реальном времени.
Учимся делать валидацию форм красиво, без традиционной для таких случаев боли:
Ну и в третьих. Самое интересное в этом паттерне вовсе не тот очевидный факт, что он устраняет ненужные коллбэки. А то, что он позволяет полностью отделить (и инкапсулировать) способ, которым выполняется data binding, как от слоя view, так и от слоя данных. Чего вообще ни один из популярных фреймворков не может.
Что, например, позволяет нам легко и непринужденно работать со сложным состоянием в React State, без какой-либо черной магии и кучи сторонних библиотек.
Учимся работать со сложным состоянием:
Comments:
Руководство по two-way data binding в React.
какие-то убойные ссылки вы подсунули, не просто браузер схлопывается а весь айпад перегружается 🙂
реакт я не видела, а ангулар меня не впечатлил, хотя мы взяли оттуда пару идей
но наш подход propriatery и вряд ли он когда выйдет за пределы компании
Edited at 2016-06-05 01:05 pm (UTC)
> видимо пора выходить на публику с нашим подходом
Выходите на здоровье, за чем дело встало. Публика оценит. Только в своих постах, пожалуйста.
Edited at 2016-06-05 05:09 pm (UTC)
мучайтесь дальше с вашим реактом 🙂
Нахуй пошел из моих комментов. Вместе со своими блевничками, фреймворками, самомнением, и оценочными суждениями. Вежливости и профессиональному любопытству он меня учить собрался, смотрите. 🙂
Edited at 2016-06-05 09:09 pm (UTC)
А нормальным людям я должен напомнить о политике комментариев здесь.
Edited at 2016-06-08 06:26 am (UTC)
Выглядит, конечно симпатично, но есть вопрос:
И в качестве оффтопика: пробовали ли вы mobx? Мы в текущий проект его засунули, и он вроде и работает, но реактивность местами создает неожиданные трудности (например, при копировании объектов реактивность теряется и нужно делать закат солнца вручную).
Можно вынести разделяемый стейт в состояние корневого компонента, и передавать вниз линки на его части (как в статье номер 3). Но в целом да. Большое приложение на одних линках собирать мягко говоря не очень удобно. Потребуется стейт-контейнер, который может побольше, чем raw react component state.
И он у нас есть. Вот он: https://github.com/Volicon/NestedTypes А вот его привязка к React, где он используется вместо React state. https://github.com/Volicon/NestedReact Линки в данном случае делаются на его элементы.
> И в качестве оффтопика: пробовали ли вы mobx?
Помимо определения глубоких изменений (которые у нас определяются по другому, и обладают транзакционной семантикой, в рамках которой наблюдатели могут добавлять к транзакции изменения, и это будет определено как одно изменение), NestedTypes:
— содержит механизм сериализации, который умеет, в частности, работать с рекурсивными данными вроде деревьев, и отношениями по id. https://github.com/Volicon/NestedTypes/blob/master/docs/RelationsGuide.md
— является «динамически типобезопасным». То есть, он при присваивании в аттрибуты приводит типы, так, что сломать протокол невозможно. Например, если аттрибут Boolean, то там будет всегда лежать Booolean. И на сервер всегда уйдет Boolean.
В наших продуктах (это здоровенный SPA на 100К строк кода) ни flux, ни React state вообще не используется. Только вот это, как единая техника работы с состоянием.
Edited at 2016-06-06 10:39 pm (UTC)
Two-way Binding Helpers
Importing
LinkedStateMixin is an easy way to express two-way binding with React.
In React, data flows one way: from owner to child. We think that this makes your app’s code easier to understand. You can think of it as “one-way data binding.”
However, there are lots of applications that require you to read some data and flow it back into your program. For example, when developing forms, you’ll often want to update some React state when you receive user input. Or perhaps you want to perform layout in JavaScript and react to changes in some DOM element size.
In React, you would implement this by listening to a “change” event, read from your data source (usually the DOM) and call setState() on one of your components. “Closing the data flow loop” explicitly leads to more understandable and easier-to-maintain programs. See our forms documentation for more information.
LinkedStateMixin is just a thin wrapper and convention around the onChange / setState() pattern. It doesn’t fundamentally change how data flows in your React application.
LinkedStateMixin: Before and After
Here’s a simple form example without using LinkedStateMixin :
This works really well and it’s very clear how data is flowing, however, with a lot of form fields it could get a bit verbose. Let’s use LinkedStateMixin to save us some typing:
valueLink objects can be passed up and down the tree as props, so it’s easy (and explicit) to set up two-way binding between a component deep in the hierarchy and state that lives higher in the hierarchy.
Note that checkboxes have a special behavior regarding their value attribute, which is the value that will be sent on form submit if the checkbox is checked (defaults to on ). The value attribute is not updated when the checkbox is checked or unchecked. For checkboxes, you should use checkedLink instead of valueLink :
There are two sides to LinkedStateMixin : the place where you create the valueLink instance and the place where you use it. To prove how simple LinkedStateMixin is, let’s rewrite each side separately to be more explicit.
18 – Adding Two Way Binding in React
React – The Complete Guide (incl. React Router 4 & Redux)
Getting Started
Understanding the Base Features Syntax
Working with Lists and Conditionals
Styling React Components Elements
Dive Deeper into Components React Internals
We covered a lot and we changed a lot of names, what if we want to change the name on our own.
Data Binding in React
So let’s that in the Person component. we also have an another element a normal input element, a normal input element which is type of text.
onChange=<> : we can listen to a special event on change. onChange will be fired whenever the value in the input changes.
and there i dont want to execute some method which i need to pass down from our src/App.js file.
We got that switch name handler and we will leave it as it is and instead add a new handler, will name as a nameChangedHandler which expect to get an event object that we haven’t used before, but in there I still want to change the state now of course theoretically you would want to change does it state or the name of the person for which we type this. This is something we’ll do it later in the course once we learned how to correctly render a list of dynamic elements.
So for now i will always change the name in the App.js
The event object will be passed to it automatically by React like a normal javascript where you all by default get access to the event object.
With that let us save the code and see what happens in your browser.
with that let’s save this and let us see what happens we got input below all components but for most of them, nothing happens. but if we change input below Max details the data gets updated.
this is because we bound onChange to those props.changed which holds a reference to the nameChangedHandler and then we used the default event object to extract the target which is input element and then the value of the target which is what we entered.
This show is two things how we can dynamically update something, dynamically call an event and use the things we learn before like passing down event references or method references but it all just shows us how we can handle inputs.
Two Way Binding in React
Now it would be nice if we would see the current value of the name in the input right from the start.
So we want to set up two-way binding when we change it we want to propagate that change so that we can update the state but we also want to see the current state right from the start.
To do that we can set value=
And now we have our own two way binding setup. We listen to change, calls the method in end which refers to the nameChangedHandler which updates the state and then passed down the state to the Person with name and age and we output the name as the value of the input.