codama-idl-codama/packages/nodes/docs/discriminatorNodes/FieldDiscriminatorNode.md

FieldDiscriminatorNode

This node represents a byte discrimination strategy where the data is identified by the default value of a struct field at a given offset. Discriminator nodes are used to distinguish between different types of accounts or instructions in a program.

Attributes

Data

Attribute	Type	Description
kind	"fieldDiscriminatorNode"	The node discriminator.
field	CamelCaseString	The name of the StructFieldTypeNode we should use to identify the data.
offset	number	The byte at which the field should be located.

Children

This node has no children.

Functions

fieldDiscriminatorNode(field, offset?)

Helper function that creates a FieldDiscriminatorNode object from a field name and an optional offset.

const node = fieldDiscriminatorNode('accountState', 64);

Examples

An account distinguished by a u32 field at offset 0

accountNode({
    data: structTypeNode([
        structFieldTypeNode({
            name: 'discriminator',
            type: numberTypeNode('u32'),
            defaultValue: numberValueNode(42),
            defaultValueStrategy: 'omitted',
        }),
        // ...
    ]),
    discriminators: [fieldDiscriminatorNode('discriminator')],
    // ...
});

An instruction disctinguished by an 8-byte argument at offset 0

instructionNode({
    arguments: [
        instructionArgumentNode({
            name: 'discriminator',
            type: fixedSizeTypeNode(bytesTypeNode(), 8),
            defaultValue: bytesValueNode('base16', '0011223344556677'),
            defaultValueStrategy: 'omitted',
        }),
        // ...
    ],
    discriminators: [fieldDiscriminatorNode('discriminator')],
    // ...
});