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Output variables

docs/src/calling-contracts/variable-outputs.md

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Output variables

<!-- This section should explain variable outputs --> <!-- variable_outputs:example:start -->

Sometimes, the contract you call might transfer funds to a specific address, depending on its execution. The underlying transaction for such a contract call has to have the appropriate number of variable outputs to succeed.

<!-- variable_outputs:example:end -->

Let's say you deployed a contract with the following method:

rust,ignore
{{#include ../../../e2e/sway/contracts/token_ops/src/main.sw:variable_outputs}}

When calling transfer_coins_to_output with the SDK, you can specify the number of variable outputs:

rust,ignore
{{#include ../../../examples/contracts/src/lib.rs:variable_outputs}}
<!-- This section should explain what the `with_variable_output_policy` method does --> <!-- with_variable_output_policy:example:start -->

with_variable_output_policy sets the policy regarding variable outputs. You can either set the number of variable outputs yourself by providing VariableOutputPolicy::Exactly(n) or let the SDK estimate it for you with VariableOutputPolicy::EstimateMinimum. A variable output indicates that the amount and the owner may vary based on transaction execution.

<!-- with_variable_output_policy:example:end -->

Note: that the Sway lib-std function mint_to_address calls transfer_to_address under the hood, so you need to call with_variable_output_policy in the Rust SDK tests like you would for transfer_to_address.