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Panic.catch

Panic.catchpanic_typeactionhandler

Documentation​

Executes the provided action and if a panic matching the provided type was thrown, calls the provided callback. If action executes successfully, the result of Panic.catch is the result of that action. Otherwise, if a matching panic is thrown from within the action, the result is obtained by calling the provided handler callback. Any non-matching panics are forwarded without changes.

Arguments​

  • panic_type: The expected panic type. It can either be an Enso type or a Java class.
  • action: The code to execute that potentially panics.
  • handler: The callback to handle the panics. The callback will be provided with a Caught_Panic instance encapsulating the payload of the caught panic and its stacktrace.

Examples​

Handling a specific type of panic.​

      Panic.catch Illegal_Argument (Panic.throw (Illegal_Argument.Error "Oh no!" Nothing)) error->
          "Caught an `Illegal_Argument`: "+error.payload.message

Handling any panic.​

      Panic.catch Any (Panic.throw (Illegal_Argument.Error "Oh no!" Nothing)) error->
          "Caught some panic!"

Convert a string to an integer, catching the Java NumberFormatException​

and converting it to a more Enso-friendly dataflow error.

      polyglot java import java.lang.Long
      polyglot java import java.lang.NumberFormatException
      parse str =
          Panic.catch NumberFormatException (Long.parseLong str) caught_panic->
              Error.throw (Illegal_Argument.Error "The provided string is not a valid number: "+caught_panic.payload.getMessage)