data-handling-and-processing.md

Data handling and processing

d.Set calls for complex types

You should also include error handling for d.Set calls that are not using simple (string, number, boolean) values to catch any schema mismatches.

func resourceExampleRead(ctx context.Context, d *schema.ResourceData, meta interface{}) diag.Diagnostics {
    // ... snip
    // assuming `attr` is a map or list of types.


    if err := d.Set("my_attr", attr); err != nil {
      return fmt.Errorf("failed to set my_attr: %w", err)
    }

    return nil
}

expand* style functions

Methods that start with expand* are used for taking a schema representation and converting the data to a usable Golang struct.

This type of method will accept a map[string]interface{} or []interface{} and return a concrete type for use in API calls or interacting with the underlying Go library.

func expandThing(tfMap map[string]interface{}) *cloudflare.Thing {
    if tfMap == nil {
        return nil
    }

    apiObject := &cloudflare.Thing{}

    // ... nested attribute handling ...

    return apiObject
}

func expandThings(tfList []interface{}) []*cloudflare.Thing {
    if len(tfList) == 0 {
        return nil
    }

    var apiObjects []*cloudflare.Thing

    for _, tfMapRaw := range tfList {
        tfMap, ok := tfMapRaw.(map[string]interface{})

        if !ok {
            continue
        }

        apiObject := expandThing(tfMap)

        if apiObject == nil {
            continue
        }

        apiObjects = append(apiObjects, apiObject)
    }

    return apiObjects
}

flatten* style functions

Methods that start with flatten* are used for taking a Golang struct and converting the data to the Terraform schema representation.

This type of method will accept a Golang struct and usually returns a map[string]interface{} or []interface{} for use in d.Set() calls.

func flattenThing(apiObject *cloudflare.Thing) map[string]interface{} {
    if apiObject == nil {
        return nil
    }

    tfMap := map[string]interface{}{}

    // ... nested attribute handling ...

    return tfMap
}

func flattenThings(apiObjects []*cloudflare.Thing) []interface{} {
    if len(apiObjects) == 0 {
        return nil
    }

    var tfList []interface{}

    for _, apiObject := range apiObjects {
        if apiObject == nil {
            continue
        }

        tfList = append(tfList, flattenThing(apiObject))
    }

    return tfList
}