Function get_variable_size_field_optional 

pub fn get_variable_size_field_optional<const N: usize, F>(
    field_code: i32,
    host_fn: F,
) -> Result<Option<([u8; N], usize)>>
where
    F: FnOnce(i32, *mut u8, usize) -> i32,

Optional variant of get_variable_size_field.

Returns None if the field is not found, otherwise behaves identically to the required variant.

Type Parameters

• N - The maximum size of the buffer (compile-time constant)
• F - The type of the host function closure

Arguments

• field_code - The field code identifying which field to retrieve
• host_fn - A closure that calls the appropriate host function

Returns

Returns Result<Option<([u8; N], usize)>> where:

• Ok(Some((buffer, len))) - If the field is present
• Ok(None) - If the field is not found
• Err(Error) - If there’s an error retrieving the field

Example

let result = get_variable_size_field_optional::<48>(
    field_code,
    |fc, buf, size| unsafe { get_current_ledger_obj_field(fc, buf, size) },
)?;