Swift Promise & REST API Delegate?

[frizzy75]

I'm struggling to create a Swift class that fetches data from the Salesforce REST API. The class conforms to Salesforce's REST API delegate protocol, and implements callback methods - so I need to fulfill or reject the promise from those methods, but don't know how. Thanks in advance for any help.

import Foundation
import PromiseKit

class SalesforceObjectFetcher: NSObject, SFRestDelegate {

    var promise: Promise<SalesforceObject>!

    func fetch (request: SFRestRequest) -> Promise<SalesforceObject> {
        SFRestAPI.sharedInstance().send(request, delegate: self)
        promise = Promise<SalesforceObject>({ (fulfill, reject) -> Void in
            //TODO
        })
        return promise
    }

}

//MARK: SFRestDelegate compliance
extension SalesforceObjectFetcher {

    func request(request: SFRestRequest!, didFailLoadWithError error: NSError!) {
        //TODO: need to reject promise from here...
    }

    func request(request: SFRestRequest!, didLoadResponse dataResponse: AnyObject!) {
        //TODO: need to fulfill promise from here after converting NSDictionary response to model objects...
    }

    func requestDidCancelLoad(request: SFRestRequest!) {
        //TODO: need to reject promise from here...
    }

    func requestDidTimeout(request: SFRestRequest!) {
        //TODO: need to reject promise from here...
    }
}

[frizzy75]

I found an example in UIAlertView+Promise.swift - but also read the warning in the docs against combining promises and delegates, so closing this. Would still welcome any examples or suggestions how to do this better. Thanks.

[mxcl]

You can do this, it's still hacky, but it is an alternative.

import Foundation
import PromiseKit

class SalesforceObjectFetcher: NSObject {

    // the type of the promise might be different, see fulfill usage to decide
    let deferred = Promise<SalesforceObject>.defer()

    init() {
        deferred.promise.finally {
            println(self)  // here we force a retain on self inside the promise object
                                // it will be released once processed
        }
    }

    func fetch (request: SFRestRequest) -> Promise<SalesforceObject> {
        SFRestAPI.sharedInstance().send(request, delegate: self)
        return deferred.promise
    }
}

//MARK: SFRestDelegate compliance
extension SalesforceObjectFetcher: SFRestDelegate {

    func request(request: SFRestRequest!, didFailLoadWithError error: NSError!) {
        deferred.reject(error)
    }

    func request(request: SFRestRequest!, didLoadResponse dataResponse: AnyObject!) {
        deferred.fulfill(dataResponse as SalesforceObject)
    }

    func requestDidCancelLoad(request: SFRestRequest!) {
        let error = NSError(…)  // make a code and domain to represent this error state
        deferred.reject(error)
    }

    func requestDidTimeout(request: SFRestRequest!) {
        let error = NSError(…)
        deferred.reject(error)
    }
}

[frizzy75]

Thank you!

[frizzy75]

@mxcl - I'm curious: why the println(self) to force a retain vs. PMKRetain( ) and PMKRelease( ) ?
Thanks

[mxcl]

PMKRetain is better, I didn't suggest it because the suggestion is easier to understand, but if you understand the macros, use them!

[chkpnt]

I don't see PMKRetain / PMKRelease in the current release. Was it renamed at some time?

[mxcl]

They were never public API. So they gone. But there's other ways to achieve the same.