Global Object Identification in GraphQL

Global Object Identification in GraphQL is a crucial concept that enables precise data retrieval from APIs by using unique identifiers. It enhances the efficiency of GraphQL schemas by allowing developers to fetch specific data easily.

By defining a node interface and implementing it in object types, developers can effectively retrieve desired information, making GraphQL a powerful tool for querying and manipulating data. In this article, we will learn about Global Object Identification in GraphQL by understanding their needs, Implementation in depth with the help of examples, and so on.

• A schema is defined in GraphQL to fetch the data from the service. GraphQL schema follows the structure to retrieve and display the data.
• Service contains a huge set of data for the defined schema structure. If we want to retrieve the particular data from the service then we can fetch those data or objects via node.
• This node field has to pass on the global query of the object to retrieve the response. This is called Global Object Identification. Let’s discuss this in the following topics with examples.

• The main purpose of global object identification is to retrieve the data of the particular object type in the APIs. APIs consist of a lot of object types and fields.
• If we just want to retrieve the data of the particular fields then we can use this implementation.
• It is also helpful in retrieving information on the fields of the object type like whether the field is null or not, the data type of the field, and so on.

For example, there are 5 student’s details in the service. A GraphQL schema is defined to retrieve the data of those students. If we just want to retrieve the data of a particular student then we can pass any one of the unique fields to the global object type to retrieve the data of that particular student.

Global object identification query in GraphQL can be achieved by creating a node interface. With the help of this node interface creation, we can achieve this implementation and it will fetch the expected results with what we have passed in the global object type query. Let us discuss how to define and implement a node interface.

Defining Node interface

Before defining a node interface, we can discuss the node interface and its syntax definition along with an example.

What is Node?

A node is an interface that needs to be defined to pass it on to the global object query to retrieve the particular response from the service. The node contains any number of fields. Those fields can also be mentioned and passed on to the global object query to retrieve the information. The node must have one field at least.

Syntax:

interface Node_Name {
field_name : field_type 
}

Example of Node Interface

Create a node interface with roll_number field.

interface Node {
roll_number : ID!
}

Explanation: Here, interface is a keyword to declare the Node. roll_number is the global object that needs to be passed on the global query to retrieve the response. This roll_number shouldn’t be null. ‘ ! ‘ declares non_null to the field.

We can pass the node interface to the __type query to retrieve the response of the object type. The process of passing the interface on the global object type to retrieve the response for the defined GraphQL schema is called introspection. __type is one of the GraphQL introspection queries to retrieve the schema details.

Example:

For example, the below GraphQL schema __type query is defined with passing the node interface. The node interface is already defined in the above example. We have to pass the name of the interface to the __type along with some of the fields.

Query:

__type (name : "Node")
{
name 
kind
fields{
name 
type {
kind 
}
}
}
}

Response:

{
"__type" : {
"name" : "Node", //name of the interface
"kind" : "Interface", //type of the argument passed
"fields": [
{
"name" : "roll_number", //roll_number field which is declared in the interface body
"type" : {
"kind" : "non_null", // field is non_null
}
}
]
}
}

Explanation: The above object type receives the node interface and returns the response of the node interface in the below format.

The aim of passing the node interface in queries is to retrieve the service data of the field. It’s helpful for developers to know about the actual data of the requested node interface.

In the above example, we just got to know what is the actual type and kind of the interface field. If we want to retrieve the data of the particular student like name, age etc., then it will be done by implementing the node with object type.

Syntax:

interface Node_Name {
field_name : field_type
}
type type_name implements Node_Name {
field_name : field_to_be_displayed
}

Example: Display the particular student information

Let’s create the node interface with the global field to be passed on the query. Now, implement the node interface with the type Student and specified fields to be displayed in the response.

Query:

interface Node {
roll_number : ID !
}
type Student implements Node {
name : name !
age : age !
}

Now, if we want to retrieve the particular student data then pass the roll_number of that student to get the response.

Pass it in the below format query. studentNode is user defined query.

{
studentNode : Node (roll_number : "14CSE")
{
  roll_number
  ... on Student {
     name 
     age
}
}
}

If we execute the above query then you will get the response of the particular student in the below format.

Response:

{
"studentNode" :
{
"roll_number" : "14CSE",
"name" : "John Alan",
"age" : "15",
}
}

Explanation: If you execute the above query then you will get the response of the particular student in the below format.

Overall, Global Object Identification in GraphQL is a crucial mechanism for efficiently retrieving specific data from APIs. By defining and implementing node interfaces, developers can effectively query and retrieve targeted information, enhancing the flexibility and usability of GraphQL schemas. This approach enables developers to streamline data retrieval processes, improve application performance, and create more dynamic and responsive GraphQL APIs.