The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. How to get the src from image object? I'm newbie in react native and react js.
Please help me to get the image src. Let's say the data is assigned to variable data As you can see the JSON start with array so you will have to access the content in the array.
In this case the array only have 1 content. So, if you access datayou will get. Learn more. How to get objects of objects in react native? Ask Question. Asked 1 year, 7 months ago.
Active 1 year, 7 months ago. Viewed 1k times. Ramesh Ramesh 31 8 8 bronze badges. Active Oldest Votes. You have to replace the this. Bhuvana C Bhuvana C 33 7 7 bronze badges. Billy Koswara Billy Koswara 3 3 silver badges 20 20 bronze badges. Sign up or log in Sign up using Google. Sign up using Facebook.
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I am stuck with a very simple problem. I have login form with username, password and button. In my button handler, I try to get the textinput value. But always get undefined value. Am I missing something? The quick and less optimized way to do this is by using arrow function inside your onChangeText callback, by passing username as your argument in your onChangeText callback. Or if you are using es6 class property shorthand which autobinds this.
But this has drawbacks, when it comes to testing and performance. Read More Here. If you are like me and doesn't want to use or pollute state for one-off components here's what I did:. You should use States to store the value of input fields. This piece of code worked for me. What I was missing was I was not passing 'this' in button action:. Learn more. Asked 4 years, 6 months ago. Active 4 months ago. Viewed k times.
WayneZhao WayneZhao 1, 3 3 gold badges 10 10 silver badges 8 8 bronze badges. Active Oldest Votes.After building your component, you may find yourself wanting to "reach out" and invoke methods on component instances returned from render. In most cases, this should be unnecessary because the reactive data flow always ensures that the most recent props are sent to each child that is output from render.
However, there are a few cases where it still might be necessary or beneficial, so React provides an escape hatch known as refs.
These refs references are especially useful when you need to find the DOM markup rendered by a component for instance, to position it absolutelyuse React components in a larger non-React application, or transition your existing codebase to React. Keep in mind, however, that the JSX doesn't return a component instance! It's just a ReactElement : a lightweight representation that tells React what the mounted component should look like.
This should only ever be used at the top level. Inside components, let your props and state handle communication with child components, or use one of the other methods of getting a ref string attribute or callbacks. React supports a special attribute that you can attach to any component.
The ref attribute can be a callback function, and this callback will be executed immediately after the component is mounted. The referenced component will be passed in as a parameter, and the callback function may use the component immediately, or save the reference for future use or both.
It's as simple as adding a ref attribute to anything returned from render :. In the latter case, you can call methods on that component if any are exposed in its class definition. Note that when the referenced component is unmounted and whenever the ref changes, the old ref will be called with null as an argument.
This prevents memory leaks in the case that the instance is stored, as in the second example. Also note that when writing refs with inline function expressions as in the examples here, React sees a different function object each time so on every update, ref will be called with null immediately before it's called with the component instance.
Although string refs are not deprecated, they are considered legacy, and will likely be deprecated at some point in the future. Callback refs are preferred.
In some other code typically event handler codeaccess the backing instance via this. In order to get a reference to a React component, you can either use this to get the current React component, or you can use a ref to get a reference to a component you own. They work like this:. In this example, we get a reference to the text input backing instance and we call focus when the button is clicked.
For composite components, the reference will refer to an instance of the component class so you can invoke any methods that are defined on that class. Refs are a great way to send a message to a particular child instance in a way that would be inconvenient to do via streaming Reactive props and state.
They should, however, not be your go-to abstraction for flowing data through your application. By default, use the Reactive data flow and save ref s for use cases that are inherently non-reactive. Guides Why React?AsyncStorage is an unencrypted, asynchronous, persistent, key-value storage system that is global to the app. It should be used instead of LocalStorage. It is recommended that you use an abstraction on top of AsyncStorage instead of AsyncStorage directly for anything more than light usage since it operates globally.
On iOS, AsyncStorage is backed by native code that stores small values in a serialized dictionary and larger values in separate files. Each method in the API returns a Promise object.
Fetches an item for a key and invokes a callback upon completion. Returns a Promise object. Sets the value for a key and invokes a callback upon completion. Removes an item for a key and invokes a callback upon completion.
Merges an existing key value with an input value, assuming both values are stringified JSON. Erases all AsyncStorage for all clients, libraries, etc. You probably don't want to call this; use removeItem or multiRemove to clear only your app's keys.
Gets all keys known to your app; for all callers, libraries, etc. This allows you to batch the fetching of items given an array of key inputs. Your callback will be invoked with an array of corresponding key-value pairs found:. Use this as a batch operation for storing multiple key-value pairs. When the operation completes you'll get a single callback with any errors:. Call this to batch the deletion of all keys in the keys array.
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 tried using ListView inside a Picker object, but when I navigate to that page. You don't need to use listview within picker. Learn more. React Native apply array values from state as Picker items Ask Question. Asked 3 years ago.
Active 1 year, 3 months ago. Viewed 20k times. I have an array in my state named Categories. These are its values: ['Food', 'Home', 'Savings']. My goal is that I need them to be rendered as Picker. How is that possible? MarianD 5, 6 6 gold badges 21 21 silver badges 35 35 bronze badges. Active Oldest Votes. Freddy 82 1 1 gold badge 1 1 silver badge 12 12 bronze badges.
Manjeet Singh Manjeet Singh 2, 2 2 gold badges 18 18 silver badges 32 32 bronze badges. Hello Sir, Thank You for the solution, It worked, but it alerted warnings. It says 'React.
The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. New to React and trying to loop Object attributes but React complains about Objects not being valid React children, can someone please give me some advice on how to resolve this problem? I've added createFragment but not completely sure where this needs to go or what approach I should take?
The problem is the way you're using forEachas it will always return undefined. You're probably looking for the map method, which returns a new array:. If you're writing ES6, you can accomplish the same thing a bit neater using an arrow function :. I highly suggest you to use an array instead of an object if you're doing react itteration, this is a syntax I use it ofen. Read more here. If your looking for itteration, this is the way to do it.
Learn more. How to loop an object in React? Ask Question. Asked 3 years, 6 months ago. Active 6 months ago. Viewed k times. I got a similar error like this before. This was interesting also: stackoverflow. Active Oldest Votes.
Banzy Banzy 5 5 bronze badges. When using an object, the keys are often IDs rather than indexes. If, however, the keys are all indexes, I agree with you. I appreciate your comment, but I'm not talking about an objects. Working with array seems the best for me and it's also good provided by the docs.
Keys are not neccessary at all, they are meant to keep the order of your elements. Arrays are not always the best choice, even though they often are.
When caching stuff e. And while React will add keys, based on indexes, when you don't provide them explicitly, there're definitely use cases for doing so. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown.
React Native Passing Value between Screen
The Overflow Blog. The Overflow How many jobs can be done at home?While creating an app containing multiple screens, then sometimes it is required to pass value between one screen to another. This can be achieved by using this. Before diving into this example, you need to first go through React Native Navigation. The value param is passed as an object in the first screen to the navigation. Create a HomeScreen. The TextInput component has an onChangeText prop which takes a function which is to be called whenever the text changed.
In the above code userName: this. On clicking the Button userName and otherParam is passed to Profile screen. In this screen, we receive the value of userName and otherParam using navigation. Create the App. The HomeScreen set as the first screen using the initialRouteName. JavaTpoint offers too many high quality services. Mail us on hr javatpoint. Please mail your requirement at hr javatpoint. Duration: 1 week to 2 week. React Native Tutorial.
AsyncStorage AsyncStorage Methods. Ionic React Native vs. Spring Boot. Selenium Py. Verbal A. Angular 7. Compiler D.React Tutorial - Learn React - React Crash Course 
Software E. Web Tech. Cyber Sec. Control S. Data Mining. Javatpoint Services JavaTpoint offers too many high quality services. This function is used to navigate between the different screens.
Example In this example, we will input the value in the first screen and get it into the second screen.