Graphql optional fields

Nest provides several utility functions that perform type transformations to make this task more convenient. When building input validation types also called DTOsit's often useful to build create and update variations on the same type. For example, the create variant may require all fields, while the update variant may make all fields optional.

Nest provides the PartialType utility function to make this task easier and minimize boilerplate. The PartialType function returns a type class with all the properties of the input type set to optional. For example, suppose we have a create type as follows:. By default, all of these fields are required. To create a type with the same fields, but with each one optional, use PartialType passing the class reference CreateUserInput as an argument:.

The PartialType function takes an optional second argument that is a reference to the decorator factory of the type being extended. In the example above, we are extending CreateUserInput which is annotated with the InputType decorator.

We didn't need to pass InputType as the second argument since it's the default value. If you want to extend a class decorated with ObjectTypepass ObjectType as the second argument. For example:. The PickType function constructs a new type class by picking a set of properties from an input type. For example, suppose we start with a type like:. We can pick a set of properties from this class using the PickType utility function:.

The OmitType function constructs a type by picking all properties from an input type and then removing a particular set of keys. We can generate a derived type that has every property except email as shown below. In this construct, the second argument to OmitType is an array of property names. The type mapping utility functions are composable.

For example, the following will produce a type class that has all of the properties of the CreateUserInput type except for emailand those properties will be set to optional:. Nest is an MIT-licensed open source project. It can grow thanks to the support by these awesome people. If you'd like to join them, please read more here. Subscribe to stay up to date with the latest Nest updates, features, and videos!

Standalone apps. Migration guide. T-Shirts and Hoodies. Support us. Mapped types Partial Pick Omit Composition.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

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. None of the source files had a label field, so that schema was never touched. Having at least 1 file with label field will return a valid response. Learn more. Asked 16 days ago. Active 16 days ago. Viewed 18 times. Tha database for that queries comes up to a set of YAML files in a folder.

Not all source files defines a label field. Is it possible to return a default or empty value for that field when missing? Tom Freudenberg. Tom Freudenberg Tom Freudenberg 1, 8 8 silver badges 24 24 bronze badges. Active Oldest Votes.

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Technical site integration observational experiment live on Stack Overflow. Dark Mode Beta - help us root out low-contrast and un-converted bits. Related Hot Network Questions. Question feed.At its simplest, GraphQL is about asking for specific fields on objects. 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.

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. Oh, one more thing - the query above is interactive. That means you can change it as you like and see the new result. Try adding an appearsIn field to the hero object in the query, and see the new result. In the previous example, we just asked for the name of our hero which returned a String, but fields can also refer to Objects.

In that case, you can make a sub-selection of fields for that object. GraphQL queries can traverse related objects and their fields, letting clients fetch lots of related data in one request, instead of making several roundtrips as one would need in a classic REST architecture. Note that in this example, the friends field returns an array of items.

GraphQL queries look the same for both single items or lists of items, however we know which one to expect based on what is indicated in the schema. If the only thing we could do was traverse objects and their fields, GraphQL would already be a very useful language for data fetching. But when you add the ability to pass arguments to fields, things get much more interesting.

You can even pass arguments into scalar fields, to implement data transformations once on the server, instead of on every client separately. Arguments can be of many different types. GraphQL comes with a default set of types, but a GraphQL server can also declare its own custom types, as long as they can be serialized into your transport format. If you have a sharp eye, you may have noticed that, since the result object fields match the name of the field in the query but don't include arguments, you can't directly query for the same field with different arguments.

That's why you need aliases - they let you rename the result of a field to anything you want. In the above example, the two hero fields would have conflicted, but since we can alias them to different names, we can get both results in one request. Let's say we had a relatively complicated page in our app, which let us look at two heroes side by side, along with their friends. You can imagine that such a query could quickly get complicated, because we would need to repeat the fields at least once - one for each side of the comparison.GraphQL improves on that by having a complete schema of your available data, and giving you back exactly the fields you asked for.

A field can either be nullable or non-null, and this tells you whether or not you could receive a null value when you ask for it. By default, every field in GraphQL is nullable, and you can opt in to mark it non-null. In the following schema, we have a Restaurant type with a location field that refers to a Location type:. The fields whose types have an exclamation mark,!

So for the following query:. You can get the following results:. This means that in addition to guaranteeing the shape of the result, GraphQL can provide a guarantee for which fields must be present when queried.

The usefulness of such a guarantee becomes apparent when you think about the frontend code that might consume the result of such a query.

Imagine the following code in JavaScript:. But, once we look more closely at our schema, it turns out that there are two potential errors hidden in this code:. So a more correct version will look like:. For example:. What happens? When you try to return a null value in a resolver for a non-null field, the null result bubbles up to the nearest nullable parent. This also brings up another common question about nullability: How does it work with lists?

Non-null is also a modifier, and it turns out you can apply non-null and list modifiers in an arbitrarily nested way, especially since lists can be nested:. So what does it mean to have the non-null inside vs. Well, it decides whether the non-null applies to the list item vs the list itself. For example, you can have a List of Non-Null Strings:. For example, in JSON:.

This means that the list itself cannot be null, but it can contain null values:. Finally, we can combine the two:.GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. Have a question about this project?

graphql optional fields

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Hands-On GraphQL Tutorial Step 7: Declaring Restricted Fields in GraphQL

Unless I'm overlooking something, I'm not seeing any way to pass null into a mutation for an 'optional' arg. It seems that the keys with null values get stripped out inside GraphQL-JS itself before making it to my resolve in the obj parameter.

In GraphQL input variables, there is no difference between null and undefined. The value null means "lack of a value".

While passing null as a sentinel value to mean "delete this value" is a pattern sometimes seen in JavaScript mutation APIs, it's not one that GraphQL is well suited to directly mirror at the moment.

Does this match what you're trying to do, or is there more information you could provide about your use case? Yes, that's what I'm trying to do: delete a pre-existing [optional] value.

Queries and Mutations

Of course, deleting a required i. Since GraphQL does not have this sentinal value, I recommend a more explicit form for deleting things:. That would work. However, note that using null is also explicit. The above would be:. We do not plan on supporting this since most environments do not have different null and undefined sentinel values - that's a specific feature of JavaScript and GraphQL is designed to be supported by many more platforms.

I don't personally agree with this. Using null to implicitly mean "delete this value" is a JavaScript-ism that doesn't translate well to platform-agnostic systems. I personally much prefer the explicit deletions: field. I also like terse APIs, and when using only JavaScript often use this mechanism myself, but I fear that if we embraced this concept in GraphQL, the implicit null would be misinterpreted by different servers and result in the accidental deletion of data.

graphql optional fields

I agree that implicit null seems bad - so how about an explicit sentinel object to indicate explicit nulling? Haskell, OCaml? In these it is easy enough to pass 'None' or 'Nothing' and I would argue that the GraphQL engine shouldn't arbitrarily strip out such values whether they be NoneNothing or null [inserting itself between the user and himself].

graphql optional fields

Er, I see the sentinel object was already covered, but I missed that in reading.Nest provides several utility functions that perform type transformations to make this task more convenient. When building input validation types also called DTOsit's often useful to build create and update variations on the same type. For example, the create variant may require all fields, while the update variant may make all fields optional.

Nest provides the PartialType utility function to make this task easier and minimize boilerplate. The PartialType function returns a type class with all the properties of the input type set to optional. For example, suppose we have a create type as follows:.

By default, all of these fields are required. To create a type with the same fields, but with each one optional, use PartialType passing the class reference CreateUserInput as an argument:. The PartialType function takes an optional second argument that is a reference to the decorator factory of the type being extended. In the example above, we are extending CreateUserInput which is annotated with the InputType decorator. We didn't need to pass InputType as the second argument since it's the default value.

If you want to extend a class decorated with ObjectTypepass ObjectType as the second argument. For example:. The PickType function constructs a new type class by picking a set of properties from an input type.

For example, suppose we start with a type like:.

graphql optional fields

We can pick a set of properties from this class using the PickType utility function:. The OmitType function constructs a type by picking all properties from an input type and then removing a particular set of keys. We can generate a derived type that has every property except email as shown below.

In this construct, the second argument to OmitType is an array of property names. The type mapping utility functions are composable.

For example, the following will produce a type class that has all of the properties of the CreateUserInput type except for emailand those properties will be set to optional:. Nest is an MIT-licensed open source project. It can grow thanks to the support by these awesome people. If you'd like to join them, please read more here. Subscribe to stay up to date with the latest Nest updates, features, and videos! Standalone apps. Migration guide. T-Shirts and Hoodies. Support us. Mapped types Partial Pick Omit Composition.On this page, you'll learn all you need to know about the GraphQL type system and how it describes what data can be queried.

Since GraphQL can be used with any backend framework or programming language, we'll stay away from implementation-specific details and talk only about the concepts.

If you've seen a GraphQL query before, you know that the GraphQL query language is basically about selecting fields on objects. So, for example, in the following query:. Because 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 it's useful to have an exact description of the data we can ask for - what fields can we select? What kinds of objects might they return?

What fields are available on those sub-objects? That's where the schema comes in. Every GraphQL service defines a set of types which completely describe the set of possible data you can query on that service. Then, when queries come in, they are validated and executed against that schema.

GraphQL services can be written in any language. Since we can't rely on a specific programming language syntax, like JavaScript, to talk about GraphQL schemas, we'll define our own simple language. We'll use the "GraphQL schema language" - it's similar to the query language, and allows us to talk about GraphQL schemas in a language-agnostic way.

The most basic components of a GraphQL schema are object types, which just represent a kind of object you can fetch from your service, and what fields it has.

Queries and Mutations

In the GraphQL schema language, we might represent it like this:. The language is pretty readable, but let's go over it so that we can have a shared vocabulary:. Every field on a GraphQL object type can have zero or more arguments, for example the length field below:. All arguments are named. Unlike languages like JavaScript and Python where functions take a list of ordered arguments, all arguments in GraphQL are passed by name specifically. In this case, the length field has one defined argument, unit.

Arguments can be either required or optional. When an argument is optional, we can define a default value - if the unit argument is not passed, it will be set to METER by default. Most types in your schema will just be normal object types, but there are two types that are special within a schema:.


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