But what if you want to execute a query in response to a different event, such as a user clicking a button? When React renders a component that calls useQuery, Apollo Client automatically executes the corresponding query. If you set errorPolicy to all, useQuery does not discard query response data, allowing you to render partial results.įor more information, see Handling operation errors. In this case, Apollo Client discards any query response data returned by the server and sets the error property in the useQuery result object. The default value is none, which tells Apollo Client to treat all GraphQL errors as runtime errors. You can customize your query error handling by providing the errorPolicyĬonfiguration option to the useQuery hook.
To view a complete version of the app we just built, check out the CodeSandbox here.
To enable polling for a query, pass a pollInterval configuration option to the useQuery hook with an interval in milliseconds: Polling provides near-real-time synchronization with your server by executing your query periodically at a specified interval. Apollo Client supports two strategies for this: polling and refetching. Sometimes, you want to make sure that your query's cached data is up to date with your server's data. Next, let's learn some techniques for ensuring that our cached data is fresh. You'll notice that the bulldog photo loads instantly the second time around. Then switch to another breed, and then switch back to bulldog. Select bulldog from the dropdown to see its photo appear. In this case, we want to pass the currently selected breed from the dropdown. The variables option is an object that contains all of the variables we want to pass to our GraphQL query. Notice that we're providing a configuration option ( variables) to the useQuery hook this time. DogPhoto accepts a prop called breed that reflects the current value of the dropdown menu in our Dogs component: To see this caching in action, let's build a new component called DogPhoto. This makes later executions of that same query extremely fast. Whenever Apollo Client fetches query results from your server, it automatically caches those results locally. In the next step, we'll associate the dropdown with a more sophisticated query that uses GraphQL variables. When the user selects a dog breed from the populated dropdown, the selection is sent to the parent component via the provided onDogSelected function. The component renders a dropdown menu that's populated with the list of dog breeds returned by the server.
When loading is false and there is no error, the query has completed.As long as loading is true (indicating the query is still in flight), the component presents a Loading.Refer to 's documentation for more insight, and create your own custom component when needed.As our query executes and the values of loading, error, and data change, the Dogs component can intelligently render different UI elements according to the query's state: You might not want to use in some cases, since the implementation is basic. To handle this use case, you can use the component, which has the same props as, and add whatever children to it you would like to layer on top of it. Background Image via Nesting Ī common feature request from developers familiar with the web is background-image.
#React native photo view free
Feel free to use it as your data structure to store more information about your image. On the user side, this lets you annotate the object with useful attributes such as the dimension of the image in order to compute the size it's going to be displayed in. via flex), you may need to manually set and transparently support spriting on all the existing call sites. If you need to scale the image dynamically (i.e. Note that image sources required this way include size (width, height) info for the Image.
In order for this to work, the image name in require has to be known statically.
#React native photo view simulator
#React native photo view plus
For example,, will be used on an iPhone 7, while will be used on an iPhone 7 Plus or a Nexus 5. the bundler will bundle and serve the image corresponding to device's screen density.
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