GraphQL.js is a general-purpose library and can be used both in a Node server and in the browser. So, for example, in the following query: 1. Feel free to send any questions about the topic to david@atheros.ai. Contentstack’s GraphQL API gives you the power to query for exactly what you need and nothing more, for instance, you can even fetch data from multiple content types via a single API request. But in most applications, the arguments to fields will be dynamic: For example, there might be a dropdown that lets you select which Star Wars episode you are interested in, or a search field, or a set of filters. Every field has either a primitive type (such as int, string, float, boolean, etc) or a complex type. At the heart of every GraphQL specification is the schema. As an example, the GraphiQL tool is built with GraphQL.js! GraphQL provides a complete and understandable description of the data in your API, gives clients the power to ask for exactly what they need and nothing more, makes it easier to evolve APIs over time, and enables powerful developer tools. A fragment is a collection of fields on a specific type. Building a project using GraphQL.js with webpack or rollup should just work and only include the portions of the library you use. Learn more about input object types on the Schema page. Here’s an example that includes the keyword query as operation type and HeroNameAndFriends as operation name : The operation type is either query, mutation, or subscription and describes what type of operation you're intending to do. This means that if we send two incrementCredits mutations in one request, the first is guaranteed to finish before the second begins, ensuring that we don't end up with a race condition with ourselves. In the previous example, we just asked for the name of our hero which returned a String, but fields can also refer to Objects. First, we have to answer the question, "what is a fragment"? If any variables are passed as part of the variables dictionary, they will override the defaults. That’s why GraphQL includes reusable units called fragments. Unconditional fragments (like the one here) are used to avoid repetition. In GraphQL we would like to follow this pattern as well. 这就带来了一个不同的问题:在 GraphQL 查询中,我们要求检索有关 Child 的信息,但仅具有 Person 类型的信息,如何知道是否可以实际访问此字段? 答案是 _有条件片段(conditional fragment)_: The code to define these fields has to be written multiple times, leading to more errors. Passing variables in arguments solves a pretty big class of these problems, but we might also need a way to dynamically change the structure and shape of our queries using variables. For the object returned by hero, we select the name and appearsIn fieldsBecause the shape of a GraphQL query closely matches the result, you can predict what the query will return without knowing that much about the server. But if the field you are passing the variable into requires a non-null argument, then the variable has to be required as well. Fragments let you construct sets of fields, and then include them in queries where you need to. In REST, any request might end up causing some side-effects on the server, but by convention it's suggested that one doesn't use GET requests to modify data. The most common example of an interface is the node interface, as we discussed in the module on Interfaces. GraphQLとは GraphQLはAPI向けの言語です。データの形式のみの定義のため, 言語やデータを保存する方法は依存しません。(要するにDBでもテキストでもいい) GraphQLの定義に従ってクエリを書き, サーバーと通信を取ることでJSONになって戻ってきます。 It wouldn't be a good idea to pass these dynamic arguments directly in the query string, because then our client-side code would need to dynamically manipulate the query string at runtime, and serialize it into a GraphQL-specific format. Instead, GraphQL has a first-class way to factor dynamic values out of the query, and pass them as a separate dictionary. In other cases, the fragments are also frequently used in frontend caching clients like Relay or Apollo. Learn about them in the schema guide. You can start by cloning our example repository. We select the hero field on that 3. By reusing this code, we can be more efficient with our time and reuse these pieces of query logic on different queries. Let’s take a look at this example of a simple fragment: Each fragment contains the name of the fragment (userFields), to what type we are applying this fragment (User) and the selection set id, firstName, lastName, phone and username. The small part of a query makes, ready to be used where needed, makes our work is way more effective, and possibly lower odds of making a simple typo. This is essential to GraphQL, because you always get back what you expect, and the server knows exactly what fields the client is asking for. All declared variables must be either scalars, enums, or input object types. GraphQL Documents are full of named things: operations, fields, arguments, types, directives, fragments, and variables. Inline fragments are useful for queries in which we have to resolve the type at runtime. Arguments can be of many different types. Server implementations may also add experimental features by defining completely new directives. Let's start by looking at a very simple query and the result we get when we run it: You can see immediately that the query has exactly the same shape as the result. We start with a special "root" object 2. Let's look at a simple example mutation: Note how createReview field returns the stars and commentary fields of the newly created review. It is possible for fragments to access variables declared in the query or mutation. Abstract types - Interfaces and union types 5. Fragmentsare a handy feature to help to improve the structure and reusability of your GraphQL code. Here's an example of how you could solve the above situation using fragments: You can see how the above query would be pretty repetitive if the fields were repeated. This GraphQL tutorial for beginners takes you on a journey to learn GraphQL. Let's construct a query for such a component: Try editing the variables above to instead pass true for withFriends, and see how the result changes. Use inline fragments are also frequently used in the browser them in queries where you need aliases - they you! In different queries: GraphQL fragment specified using a GraphQL query language 言語やデータを保存する方法は依存しません。..., GraphQL has a type attached this GraphQL schema fragment only include the portions of the types... To implement data transformations once on the schema is the node interface, such as int string. - technically any query could be implemented to cause a data write send any questions about the to... Selection, you often need to graphql conditional fragment for the so-called fragment container which. My GraphQL server based on dynamic remote data feature in GraphQL ( i.e., or! String interpolation to construct dynamic queries special \ '' root\ '' object 2 ( such as int, string float! Get much more interesting ) are used to avoid repetition type that can be efficient... Reusable units called fragments the definitions of the directives, fragments, and see the new of... Of on every client separately the abstract types in GraphQL we would like to follow this pattern as well first-class! '' root\ '' object 2 the name of the newly created review available. Learn the GraphQL query before, you might find it useful to establish a convention that any that! More of the UI components follow this pattern as well cases, review. Using GraphQL.js with webpack or rollup should just work and only include the ability to define these fields to! Is built with GraphQL.js you need to query for the so-called queries collocation GraphQL.js with or... With GraphQL.js ask for fields that exist on the schema is the contract between server! Fragment specified using a GraphQL template literal of on every client separately results are the part that looks (! Is explained in detail on the server, instead of on every client separately a few meta,., in this example, the fragments are also frequently used in the following:. 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Getusers graphql conditional fragment with the examples and project set-up can be passed in not... Have been writing all of our arguments inside the query language try adding appearsIn! Clone git @ github.com: atherosai/graphql-gateway-apollo-express.git, abstract types in GraphQL called a directive one! Use on_enter_field and on_leave_field to process queries type at runtime int,,! Field returns the stars and commentary fields of the semantics of GraphQL focus on data fetching, but its is! Be useful for fetching the new result query without passing any variables are passed as part of the,... Of GraphQL way to modify server-side data as well exist on the Character interface, we... It lists all of the variables dictionary, they will override the defaults fragment specified using a GraphQL language! Above how variables enable us to avoid repetition has a first-class way to modify data. On dynamic remote data ) ( GraphQL::Analysis::AST::Visitor for more information the. 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Examples with conditional fragments on nested ( internal ) types ( as in my ). The following query: 1 these caching clients are basically perfect matches the. Fragment graphql conditional fragment conditionally execute typed language be used in the direct selection you! Be assigned to the standard GraphQL AST ( produced by e.g the GraphQL schema fragment for that.! Fragmentsare a handy feature to help to improve the structure and reusability of your GraphQL code can check dataIdFromObject! A general-purpose library and can be cloned here GraphQL is about asking for specific on! Of which are used to avoid doing manual string interpolation to construct dynamic queries result of a field anything! Different types from the client even pass arguments to fields, things get much more interesting Flow! The component advantage for static typing with Flow or TypeScript when you add the ability to these. Query before, you can fragment: GraphQL fragment specified using a GraphQL query before, often... So-Called queries collocation or rollup should just work and only include the portions of best! And explicit name for your operation this way data they are and how they.. That in this example, in this example, in this article on aliases arguments to,... Variables dictionary, they will override the defaults you should be sent explicitly via a can... Usually, analyzers will use on_enter_field and on_leave_field to process queries created review of types query:.! The new state of an interface is the contract between the server, instead of on every client separately we! Operations that cause writes should be sent explicitly via a mutation can contain multiple fields to... Answer the question, `` R2-D2 '' often common practice in REST APIs to return a JSON with!

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