Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. I am working on React-Native, i want to call a function from different class but when i am trying to do it's showing some error. But error message is coming after pressing the button in Class A, ' undefined is not a function evaluating 'B. You dont initiate your class, to solve this you need to change the B. I tried various solutions on this page but that didn't work.
I am copying a solution from another web page here. Very simple and impressive. Might help someone looking for a simple solution:. You have to create the parent with a constructor, access to super method for extend well the Component Class, then export the parent class and extend it on the Class A where you have access to this functions by this context of the class.
I can see that you are not exporting the class B, you are only importing. Please try adding an export statement at bottom of the class B file like so export default B. Import the first class in the another class where you want to use the function defined in first class. In this case, We are using a function defined in class1 to class2.
Learn more. How to call a function from another class in React-Native? Ask Question. Asked 2 years, 11 months ago. Active 11 months ago. Viewed 48k times. Class A import B from '. You're trying to use a component class directly?
You need to instantiate the class or change the method to static to be able to call it. Active Oldest Votes. Note: B class should not be a component, you can use it as a helper class.
Hussam Kurd Hussam Kurd 2, 24 24 silver badges 26 26 bronze badges. Bruno Oliveira Bruno Oliveira 81 8 8 bronze badges. I dont know why this has not been chosen as the right answer! I noticed you didn't export your class B. AnR AnR 1, 3 3 gold badges 20 20 silver badges 40 40 bronze badges. I am also trying same.
Example to Call Functions of Other Class From Current Class in React Native
Except that it's can be simpler than you explained above, yet it really helped. FPast FPast 21 1 1 bronze badge. Hope this helps.Mobile apps are rarely made up of a single screen. Managing the presentation of, and transition between, multiple screens is typically handled by what is known as a navigator. This guide covers the various navigation components available in React Native.
If you are getting started with navigation, you will probably want to use React Navigation. React Navigation provides a straightforward navigation solution, with the ability to present common stack navigation and tabbed navigation patterns on both Android and iOS. If you'd like to achieve a native look and feel on both Android and iOS, or you're integrating React Native into an app that already manages navigation natively, the following library provides native navigation on both platforms: react-native-navigation.
The community solution to navigation is a standalone library that allows developers to set up the screens of an app with a few lines of code. Next, install the required peer dependencies. You need to run different commands depending on whether your project is an Expo managed project or a bare React Native project. Then install the pods to complete the installation:. Note: You might get warnings related to peer dependencies after installation.
They are usually caused by incorrect version ranges specified in some packages. You can safely ignore most warnings as long as your app builds. To finalize installation of react-native-gesture-handleradd the following at the top make sure it's at the top and there's nothing else before it of your entry file, such as index.
Now, you need to wrap the whole app in NavigationContainer. Usually you'd do this in your entry file, such as index. In this example, there are 2 screens Home and Profile defined using the Stack. Screen component. Similarly, you can define as many screens as you like. You can set options such as the screen title for each screen in the options prop of Stack. Each screen takes a component prop that is a React component.React - How to Pass Functions between Components - Episode 22
Those components receive a prop called navigation which has various methods to link to other screens. For example, you can use navigation. The views in the stack navigator use native components and the Animated library to deliver 60fps animations that are run on the native thread. Plus, the animations and gestures can be customized.
React Navigation also has packages for different kind of navigators such as tabs and drawer.
Navigating Between Screens
You can use them to implement various patterns in your app. Inclusion Accessibility.This class would be our another class. Now we would create 2 function in this class one function without argument and second function with argument. We would also print the Sample text in these functions using Alert message.
Inside this constructor we would create object of Second class named as Obj. Object is used to call the function from another class. We are calling the another class function using our main class functions using their object. Screenshot in iOS device :. Rahul first of you just have to create class using class keyword, You are putting the export default wrong in this case. Now in your NetworkUtils. Then in your main app class you have to create the object of this class and call the function from NetworkUtils.
If you NetworkUtils. Thanks for comment Rahul, I will make this one for you to check the internet connection but you have to wait till Sunday. So, I need to refresh by myself. Anything helpful about it? Your email address will not be published.
React Native 0. SecondClassFunction. Andy K October 31, at am. Andy please explain your question more briefly? Andy K October 31, at pm.
Rahul tutorial on which topic?
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Passing Functions to Components
Function can be passed as an argument to other functions, can be returned by another function and can be assigned as a value to a variable.
Read more here. So we use that variable to invoke the function by adding parentheses at the end. One thing, If you have a function that returns a funtion and you just need to call that returned function, you can just have double paranthesis when you call the outer function. Learn more. Asked 3 years, 5 months ago. Active 5 months ago. Viewed k times. Ian Kemp Active Oldest Votes.
I would recommend NOT doing this. Your render is the source of truth for what your component is rendering. Abstracting that adds additional complexity.
Besides the fact that this answers is 3 years old I am not sure if I agree. IMHO I abstract this kind of things in separate components only if it is used in more than component. Some does it only after 3 reuses. THX for your comment on this old answer.In this article, we learn about how to call function from another class in react-native, as our project scope getting more this is more important to use another class, i. I have created one components folder in the root directory, in that, I created another.
Create ClassB. To call a method in this App. I have placed one TextInput in this js file we will call reference method onTextChange of TextInput and pass data through this method.
As you see above in changeData method firstly I save data in state and then pass this data to referenceCallback method which is previously passed from App.
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Getting started with React Native will help you to know more about the way you can make a React Native project. We are going to use react-native init to make our React Native App. Assuming that you have node installed, you can use npm to install the react-native-cli command line utility.
Open the terminal and go to the workspace and run. If you want to start a new project with a specific React Native version, you can use the --version argument:.
After the updation of React Native 0. To start with this Example you need to create a directory named pages in your project and create two files FirstPge. This is how you can pass the value from one screen to another screen. If you have any doubts or you want to share something about the topic you can comment below or contact us here.
There will be more posts coming soon. Stay tuned! Related Posts Using React Navigation 4. Now i want to know how to implement conditional operator in this. Once we entered value the value will be displayed in the next page.
If the value is empty then instead of applying an conditional operator in react navigation you can check the value before and the can generate the alert accordingly. To check the value you can take the help from the following example. You have to take the value from 2nd to 3rd again. For example you have took the value from 1st to 2nd and then take it in a variable and while navigating to 3rd you have to take the value again.
It works perfectly. Now i want to add a button in the second page that goes back to the first page. You can use the same way that you have used while switching from first screen to second screen. You can not directly send the data to the 3rd and 4th screen you have to take the data in the middle screen and pass the same from there also. You can also use async storage to store the value and you can access those values any time. Hi, when I am trying this approach, I get always default value not that one which I am sending from the first screen.
This will show you how to make a single page app and will help you to achieve your objective. Can you send me the code of the tab and stack navigation in one appCan you write the code Tab and Stack navigation using a app.
Can you please share the layout which you want to achieve on aboutreact11 gmail. This site uses Akismet to reduce spam.In the previous section, "Hello React Navigation"we defined a stack navigator with two routes Home and Detailsbut we didn't learn how to let a user navigate from Home to Details although we did learn how to change the initial route in our code, but forcing our users to clone our repository and change the route in our code in order to see another screen is arguably among the worst user experiences one could imagine.
We'll do something similar to the latter, but rather than using a window. If we call navigation. Said another way, we can only navigate to routes that have been defined on our stack navigator — we cannot navigate to an arbitrary component. So we now have a stack with two routes: 1 the Home route 2 the Details route. What would happen if we navigated to the Details route again, from the Details screen?
If you run this code, you'll notice that when you tap "Go to Details This is because we are already on the Details route. The navigate function roughly means "go to this screen", and if you are already on that screen then it makes sense that it would do nothing. Let's suppose that we actually want to add another details screen.
This is pretty common in cases where you pass in some unique data to each route more on that later when we talk about params! To do this, we can change navigate to push. This allows us to express the intent to add another route regardless of the existing navigation history. Each time you call push we add a new route to the navigation stack. When you call navigate it first tries to find an existing route with that name, and only pushes a new route if there isn't yet one on the stack.
The header provided by stack navigator will automatically include a back button when it is possible to go back from the active screen if there is only one screen in the navigation stack, there is nothing that you can go back to, and so there is no back button. Sometimes you'll want to be able to programmatically trigger this behavior, and for that you can use navigation. On Android, React Navigation hooks in to the hardware back button and fires the goBack function for you when the user presses it, so it behaves as the user would expect.
Another common requirement is to be able to go back multiple screens -- for example, if you are several screens deep in a stack and want to dismiss all of them to go back to the first screen. In this case, we know that we want to go back to Home so we can use navigate 'Home' not push! Another alternative would be navigation.