Promisekit: Promise Kit returns with multiple values

[kguerriero]

This issue is occurring with PromiseKit 6.2.4

I'm currently migrating some older code from PromiseKit 4.x to the latest release. Overall the new features especially done are fantastic. I'm having a bit of trouble converting the following statements from PromiseKit 4.x to the 6.2.4.

return Promise <Value> { seal in

self.performFirstNetworkingOperation().then { firstResponse -> Promise<(NSDictionary, NSDictionary)> in
        return self.secondNetworkingOperation().map { (firstResponse, $0)}   // If an error occurs here it can be lost 
        /* This caused the enclosing promise to reject in PromiseKit 4.x 
        return self.secondNetworkingOperation().map { (firstResponse, $0)}.catch{seal.reject($0)}
                Swift now complains that "Cannot convert return expression of type 'PMKFinalizer' to return type 'Promise<(NSDictionary, NSDictionary)>' "

                */
}.done { result in
        let (firstResponse, secondResponse) = result
        …
                seal.fulfill(value)
}.catch  { error in
        …
        seal.reject( error)
}

}

I essentially want to return multiple values and handle an error if it occurs. Is this possible with the latest changes to PromiseKit?

Thank you

[mxcl]

This is all you need:

return firstly {
    performFirstNetworkingOperation()
}.then { firstResponse in
    self.secondNetworkingOperation().map { (firstResponse, $0) }
}

[mxcl]

Wrapping promises in promises makes things harder than necessary. I suggest reading our common mis-usage guide in the Documentation appendix.