Handle Errors in Ramda Pipelines with tryCatch

Ramda

Share this video with your friends

Handling your logic with composable functions makes your code declarative, leading to code that's easy to read and easy to test. Breaking that up to wrap some risky function in a try/catch block introduces imperative code and makes it harder to maintain that declarative approach. With Ramda's tryCatch function, you can handle errors right in the middle of a composition and leave your code clean and functional. We'll also see how you can use propOr to avoid common "cannot find X of undefined" errors.

Learn Sifnos

~ 6 years ago

Maybe due to an evolution of the library (I'm using "ramda": "^0.25.0") The prop function doesn't raise error when provided undefined or an object with an undefined targeted property, so the tryCatch won't catch anything. And the error will occur on toUpper.

Here is a working example:

const getName = R.prop("name") const getUpperName = R.pipe( getName, R.tryCatch(R.toUpper, R.always("DEFAULT")), )

Robert Pearce

~ 5 years ago

@Sébastien: good point, and I believ that this error throwing was a bug. prop and propOr should now work like path and pathOr and respond with an undefined instead of a new error when given bad data.