Category: React hoc inject props typescript

React hoc inject props typescript

There are numerous tools and tutorials to help developers start writing simple React applications with TypeScript. The best practices for using TypeScript in a larger React application are less clear, however. This is especially the case when intergrating with an ecosystem of third party libraries used to address concerns such as: theming, styling, internationalization, logging, asynchronous communication, state-management, and form management.

At Clemexwe develop computational microscopy applications. Overall, we are very pleased with the end result.

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The consensus is that our codebase is now easier to understand and maintain. That said, our transition was not without some challenges. This article dives into some of the challenges we faced and how we overcame them. The challenges are primarily related to understanding the type signatures of the React API, and particularly those of higher order components.

How can we resolve type errors correctly, while retaining the advantages of TypeScript? This article attempts to address how to most effectively use TypeScript with React and the ecosystem of supporting libraries.

A TypeScript program can easily import any JavaScript library. Luckily, TypeScript makes it easy to define type annotations for JavaScript libraries, in the form of type declaration files. Only a few projects today offer TypeScript type definitions directly with the project.

However, for many libraries you can usually find an up to date type-definition file in the types organization namespace. For example, if you look in the TypeScript React Template package. The only downside of using external type declarations is that it can be a bit annoying to track down bugs which are due to a versioning mismatch, or subtle bugs in type declaration files themselves.

One of the main advantages of using TypeScript in a React application is that the compiler and the IDE, if configured correctly can validate all of the necessary properties provided to a component. It can also check that they have the correct type. This replaces the need for a run-time validation as provided by the prop-types library.

With React you can define a new component in two ways: as a function or as a class. The types of these two kinds of components are:. A class has a special type, which is separate from the type of instance of a class. It is defined in terms of a constructor function. Understanding this is key to understanding type signatures and some of the type errors that may arise. A ComponentClass is the type of a constructor function that returns an object which is an instance of a Component.

With some details elided, the essence of the ComponentClass type definition is:. A StatelessComponent also known as SFC is a function that takes a properties object, optional list of children components, and optional context object. It returns either a ReactElement or null.Higher-order components and monad have something in common, both sound esoteric, but at least higher-order component HOC is easy to explain. It is a component that returns a new component.

The reason for doing so is to provide shared functionality to multiple components. The React documentation has a lot of content on caveats, conventions, and examples.

In this blog post, I'll focus more on an implementation using TypeScript. HOCs are used to address cross-cutting concerns which is a fancy term for shared functionality. Examples of cross-cutting concerns in software development are logging, security, data transfer, etc. Most of the HOCs come from 3rd party libraries.

Many popular React libraries are using HOCs, for example, react-redux or i18next-react. Because many libraries already solve the issue at hand, custom HOCs, in my experience, are implemented quite rarely. The last line is important. HOC will create a component which will add translation functionality to the TranslatableView. The token, in this case, was a security token created by ASP. After dispatching Redux actions that will do the call to the API endpoint, I noticed repetition in the source code.

One of the often repeated code blocks was getting the token and placing it the action payload. I didn't want to use a singleton or global state to provide the token as it would make the code harder to test.

Instead, I took it from the Redux store and explicitly added to the requests that needed it. The idea of this snippet is to get the token from the store state mapStateProps and when dispatching mapDispatchToProps an action add it to the payload. I can make sure that wrapped component props contain token by forcing its props to implement WithToken interface. Comp parameter is the component that will receive the shared functionality.

Using the HOC is easy.

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Instead of using directly a component called MyComponentI use the wrapped version. This will ensure type-safety of the token and makes it explicit that token is required in this context. I highly recommend reading the React documentation's chapter on higher-order functions as several caveats might not be obvious, for example, a section called "Don't Use HOCs Inside the render Method" describes one of them.

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After reading the chapter, I made some changes to my code also. Even though I enjoy using TypeScript, HOCs type definitions sometimes make by head hurt as the usage of the type system is quite advanced. Hi there! If you're interested in freelancing, you should check my email list How to get started as a freelancer. In my email list, I share private learnings from my own journey, including information about pricing, finding clients, working with the clients, how to get started, etc.

react hoc inject props typescript

Please don't hesitate to reach out by sending an email or via Twitter. August 25, reacttypescript.Several months ago I wrote a guide for comparing React prop types to their equivalent TypeScript definitions and it has become super popular by those googling for how to migrate their prop types over to TypeScript.

Now I want to begin to showcase more advanced prop patterns using TypeScript. The first pattern I want to talk about is conditional React props with TypeScript.

React Higher-Order Components in TypeScript made simple

This is when you have a prop which should only be set when another prop has a specific value. Some example configurations would look like:. It may very well be an accidental error:. So the question is: how can we create this dependent relationship between two props using TypeScript? How can we make it so the two configurations above throw TypeScript errors?

Well there are several ways to do this, but this is my favorite approach:. CommonProps is your typical props definition in TypeScript.

react hoc inject props typescript

In addition to children there might be sizecolorfontetc. TruncateProps is where the magic happens. The first part of the discriminated union is when the truncate prop is false or unspecified undefined.

Conditional React props with TypeScript

In this case, we want the showExpanded prop to be invalid. Therefore we define its type as neverwhich means it cannot be set. The second part is when the truncate prop is true and only true. In this case, we want to be able to configure the showExpanded prop.

Therefore we define its type as an optional boolean. We defined the combinations individually instead of just saying that both truncate and showExpanded are optional booleans. Props is the combination of the two types.Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

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react hoc inject props typescript

Actual behavior: Throws an error highlighting the WrappedComponent in the render method. This is pretty much the same sample example used inbut with the difference, that the props of the returned component differ from the generic.

This does not seem to be possible anymore. Related Issues: The text was updated successfully, but these errors were encountered:. I believe I'm having the exact same problem on TypeScript 3. In my case I have a HOC that grabs WrappedComponent 's children to render it in a different way, forwarding all props but children to WrappedComponentresulting in the exact same error hpohlmeyer mentioned. Just for the sake of completeness: In some cases we do not remove the prop from the returned component, but make it optional instead.

This also fails for the same reason:. I just wanted to provide another example where TypeScript does not recognize that the type is assignable to T. This could be harder to solve then the original one though.

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It looks like the same problem as in It fails even if no spread rest. Starting with 3. I think that this issue can be closed, since the implicit types of the spread operator were changed. This is a fully working example you can use with TS 3. I'm not sure if this is specific to my environment lvkinsbut I was getting 'keyof T2 does not satisfy the constraint keyof T1' which dropped to 'type string is not assignable to type keyof T1'.

Fixed by specifying T1 as an extension of T Let me know if this is incorrect, am on 3. I'm kind of reviving this thread but casting is not a proper solution, it's highly unsafe. Here's a sample:.

This sample is totally valid even Component does not receive either onChange and name which are required props. We ship a massive bug due to this in our product today because of this.

This really needs to be fixed, casting is such a bad idea and I feel like I have to use it too many times. If someone has a better workaround solution, I would be happy about it. Skip to content. New issue. Jump to bottom. Milestone Backlog. Copy link. TypeScript Version: 3. I'm seeing the same thing as the original poster, but from version 3.

This would've worked in earlier TSC versions.A higher-order component HoC is a function that accepts a component as an argument and returns a new component that has been enhanced in some way. The enhanced component can add behaviour, manage state or in any other way modify WrappedComponent. A common pattern is for a higher-order component to provide some props to the wrapped component, moving the management of those props out of WrappedComponent and allowing it to focus on other concerns.

For example, connect WrappedComponent in react-redux provides props to both expose redux state and to dispatch actions. It will provide the following props to WrappedComponent. Our wrapped component will need to accept these props but it might define some others as well. In this case we want both title and className to be available on EnhancedComponent :. At this stage we have already defined the provided props as an interface and we have an example of what the wrapped component might look like.

Fairly simple: render a button containing title that toggles the expanded state. Now we want to create the enhancer function that we can use to inject isExpanded and toggleExpanded.

Our first requirement is that it accepts an argument of WrappedComponent where WrappedComponent accepts the props we want to inject. That function signature might look something like this:. ComponentType is a react type that allows you to pass in either a component class or a stateless functional component that has props of T.

Best practices for using Typescript with React

Once we have the values we need we can pass them to WrappedComponent in the render method:. This brings us on to Requirement 3 above: any other props from the wrapped component should be forwarded from the enhanced component. In this case, we really want to have the title prop be exposed on EnhancedComponent.

In fact, we need our wrapped component to accept props of both ExpanderProps and whatever else it wants. We can introduce a generic type parameter to the HoC function to represent that combined props object:. That solves our build failure: withExpander will now accept any component as long as it has the two isExpanded and toggleExpanded props. Another build failure, this time telling us that title does not exist on the enhanced component.

What we really want here is to create a new Props type that we can assign to our created component. TypeScript 2. We might want a better name though…. Now that we know what our forwarded props should look like we can specify those on the component.

Section 2: Excluding Props

The additional spread of this. Since typescript 3. As a bonus, TypeScript gives us Requirement 4 for free! Try removing title or adding an unknown property and your IDE will light up with compilation errors - thanks TypeScript! All Articles.After a discussion with my friend and colleague MarekI decided to write this guide for future reference.

I hope it helps you too. As per the official docsHOC is. They are used for extracting patterns common to multiple components into a single place, thus making the code more DRY. For the purpose of this article, we will create our own HOC ClickCounted that counts the number of clicks, and passes that count as a prop to the child component we call this the wrapped component.

It also displays the current number of clicks itself and can be styled using the style prop, similarly to a div. Finally, we can configure whether the component console. The relations between the prop types are shown on the following diagram:. The state of the HOC is simple, just the count of the clicks. As stated before, HOC is a function that takes a component and returns a component. These options are used to modify the HOC itself providing some static configuration values.

Note that those values do not have access to the props or states, they are evaluated only once when the HOC factory is called. If you need to interact with props or states from here, the only way to do it is to specify options as functions, that take the props or states as arguments.

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For ClickCounted the options are simple — a flag indicating whether to console. Having declared all the necessary types, we can write our HOC signature:. The first line starts a lambda function, that takes a single argument, that is desctructured into its keys in this case the debug key while providing the default values for them. This means the caller can call this function either without arguments, or with a single Options argument and when a value for a particular key is not provided, the specified default is used.

The second part is a generic lambda function with one type parameter TOriginalProps that represents the OriginalProps type discussed above. The lambda takes only one argument called Component note its name starts with a capital letter, this is intentional, we'll see the reason later in the text that can be one of two types:.

The props type corresponds to the diagram where two types of props are passed to the wrapped component. Then we define the class of the resulting component as having this type of props and appropriate type of state. We introduce a static property called displayName that helps to identify the component while debugging in ReactDev tools for example by telling us the name of the wrapped component as well.

Next, we define a simple constructor where we initialise the state. The handleClick method is defined that increments the click count and if debug was true in options it writes a message to console. Finally, render method is specified returning a div with style prop and a click handler specified. In the div a span with the current click count is rendered as well as the wrapped component.

This is the reason the Component argument starts with a capital letter, otherwise we wouldn't be able to render it like this.This is an HOC example for you to copy and paste. If you certain pieces don't make sense for you, head to the React HOC Docs intro to get a detailed walkthrough via a complete translation of the React docs in TypeScript.

Gil Fink - Wiring TypeScript into React - ReactNext 2018

Sometimes you want a simple way to inject props from somewhere else either a global store or a provider and don't want to continually pass down the props for it. Context is great for it, but then the values from the context can only be used in your render function. A HoC will provide these values as props. The goal is to have the props available on the interface for the component, but subtracted out for the consumers of the component when wrapped in the HoC.

Now when consuming the component you can omit the primaryColor prop or override the one provided through context. Here is a more advanced example of a dynamic higher order component that bases some of its parameters on the props of the component being passed in:.

For "true" reusability you should also consider exposing a ref for your HOC. You can use React. If this is something you need, please see the stale discussion we had and comment with your requirements. We will pick this up again if needed. React TypeScript Cheatsheet.

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react hoc inject props typescript

ReactNode. WrappedComponent : React.

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The calculated Props type here is the where the magic happens. This could be done with context instead. Component : React. Edit this page.


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