require-capability

Use require-capability to require a specific CAPABILITY to be granted before allowing the current body of code to be executed. If the required capability isn't found in the environment, the code fails to execute.

By convention, capabilities are defined using all uppercase letters.

Basic syntax

To test whether a specific CAPABILITY has been granted before executing a portion of code in a contract, use the following syntax:

(require-capability CAPABILITY)

Arguments

Use the following argument to specify the CAPABILITY to be tested for using the require-capability Pact function.

Argument	Type	Description
CAPABILITY		Specifies the capability that must be granted before executing a certain portion of code.

Return value

The require-capability function returns a boolean value indicating whether the specified CAPABILITY exists in the environment.

Examples

The following example demonstrates how to use the require-capability function to check whether the capability to transfer funds from one source to another has been granted:

(require-capability (TRANSFER src dest))

If the capability isn't found, the function fails.

The following example uses the require-capability function to create a guard that ensure both the GAS and ALLOW_GAS capabilities have been granted:

(defun gas-payer-guard ()
    (require-capability (GAS))
    (require-capability (ALLOW_GAS))
)