Ethereum: how to pass a structure/tuple to the `args` field in viem?

Passing Structures and Tuples to viem’s ​​args Field

When working with the ViEM API, you often need to pass data structures as function arguments. However, some APIs, including viem’s, require you to specify the structure of your input parameters using a specific syntax. In this article, we’ll learn how to pass structures and tuples to viem’s ​​args field.

Understanding the viem API

Before we dive into the details, let’s quickly cover some basics about the viem API:

• ViEM is an open-source media management system that provides various APIs to interact with its services.

• The util function encodeFunctionData expects a specific syntax when passing arguments. We’ll focus on that syntax in this article.

• To pass structures or tuples as arguments, you must use the args field.

encodeFunctionData syntax

The encodeFunctionData syntax is used to pass data structures as function arguments. The basic structure of an argument is:

{
"type": ,
"value": 
}

Where:

• specifies the type of value (e.g., “struct”, “tuple”).

• indicates that the value can be of any type.

Passing structures to encodeFunctionData

To pass a structure as an argument, you must create an object with two properties: type and value. Here is an example of a simple structure:

{
"type": "struct",
"value": {
"name": "MyStruct",
"fields": [
{ "name": "field1", "type": "string" },
{ "name": "field2", "type": "integer" }
]
}
}

In this example, the encodeFunctionData function will expect an object with a single field named value. This field should contain another object with two properties: type and value.

Passing tuples to encodeFunctionData

To pass a tuple as an argument, you can create an array of objects, where each object has the required fields:

{
"type": "tuple",
"value": [
{
"name": "field1",
"type": "string"
},
{
"name": "field2",
"type": "integer"
}
]
}

Putting it all together

To use the encodeFunctionData function with a structure or tuple, you need to create an object that matches its structure. Here’s an example:

const struct = {
type: "struct",
value: {
name: "MyStruct",
fields: [
{ name: "field1", type: "string" },
{ name: "field2", type: "integer" }
]
}
};
const args = {
type: "tuple",
value: [
{
name: "field1",
type: "string"
},
{
name: "field2",
type: "integer"
}
]
};
viem.encodeFunctionData(args, function(data) {
// Process the struct or tuple here
});

In this example, we create two objects: struct and args. The struct object has a single field named value, which is an array of objects with two fields each. We then use viem.encodeFunctionData to pass these objects as arguments to our function.

Conclusion

Passing structures or tuples to viem’s ​​encodeFunctionData utility requires creating objects that match its structure. By following the syntax and using examples such as those provided in this article, you should be able to successfully call functions that accept structured data as input parameters.

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