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Xcode 8.3, 9.x or 10.x / Swift 3 or 4

We recommend Carthage over CocoaPods, but both installation methods are supported.



target "Change Me!" do
  pod "PromiseKit", "~> 6.0"

If the generated Xcode project gives you a warning that PromiseKit needs to be upgraded to Swift 4.0 or Swift 4.2, then add the following:

post_install do |installer|
  installer.pods_project.targets.each do |target|
    if == 'PromiseKit'
      target.build_configurations.each do |config|
        config.build_settings['SWIFT_VERSION'] = '4.2'

Adjust the value for SWIFT_VERSION as needed.

CocoaPods are aware of this issue.


github "mxcl/PromiseKit" ~> 6.0


    .Package(url: "", majorVersion: 6)


You can just drop PromiseKit.xcodeproj into your project and then add PromiseKit.framework to your app’s embedded frameworks.

PromiseKit vs. Xcode

PromiseKit contains Swift, so there have been rev-lock issues with Xcode:

PromiseKit Swift Xcode CI Status Release Notes
6 3.1, 3.2, 3.3, 4.x 8.3, 9.x, 10.x ci-master 2018/02
5 3.1, 3.2, 3.3, 4.x 8.3, 9.x Deprecated n/a
4† 3.0, 3.1, 3.2, 3.3, 4.x 8.x, 9.x ci-master 2016/09
3 2.x 7.x, 8.0 ci-swift2 2015/10
2 1.x 7.x Deprecated 2015/10
1‡ N/A * ci-legacy

† Probably supports Xcode 10 and Swift 4.2, if not, PR welcome.

‡ PromiseKit 1 is pure Objective-C and thus can be used with any Xcode, it is also your only choice if you need to support iOS 7 or below.

We also maintain a series of branches to aid migration for PromiseKit 2:

Xcode Swift PromiseKit Branch CI Status
8.0 2.3 2 swift-2.3-minimal-changes ci-23
7.3 2.2 2 swift-2.2-minimal-changes ci-22
7.2 2.2 2 swift-2.2-minimal-changes ci-22
7.1 2.1 2 swift-2.0-minimal-changes ci-20
7.0 2.0 2 swift-2.0-minimal-changes ci-20

We do not usually backport fixes to these branches, but pull requests are welcome.

Xcode 8 / Swift 2.3 or Xcode 7

# CocoaPods
swift_version = "2.3"
pod "PromiseKit", "~> 3.5"

# Carthage
github "mxcl/PromiseKit" ~> 3.5

Using Git Submodules for PromiseKit’s Extensions

Note: This is a more advanced technique.

If you use CocoaPods and a few PromiseKit extensions, then importing PromiseKit causes that module to import all the extension frameworks. Thus, if you have an app and a few app extensions (e.g., iOS app, iOS watch extension, iOS Today extension) then all your final products that use PromiseKit will have forced dependencies on all the Apple frameworks that PromiseKit provides extensions for.

This isn’t that bad, but every framework that loads entails overhead and lengthens startup time.

It’s both better and worse with Carthage. We build individual micro-frameworks for each PromiseKit extension, so your final products link against only the Apple frameworks that they actually need. However, Apple has advised that apps link only against “about 12” frameworks for performance reasons. So with Carthage, we are worse off on this metric.

The solution is to instead import only CorePromise:

# CocoaPods
pod "PromiseKit/CorePromise"

# Carthage
github "mxcl/PromiseKit"
# ^^ for Carthage *only* have this

And to use the extensions you need via git submodules:

git submodule init
git submodule add Submodules/PMKUIKit

Then in Xcode you can add these sources to your targets on a per-target basis.

Then when you pod update, ensure that you also update your submodules:

pod update && git submodule update --recursive --remote

Release History

6.0 Feb 13th, 2018


3.0 Oct 1st, 2015

In Swift 2.0 catch and defer became reserved keywords mandating we rename our functions with these names. This forced a major semantic version change on PromiseKit and thus we took the opportunity to make other minor (source compatibility breaking) improvements.

Thus if you cannot afford to adapt to PromiseKit 3 but still want to use Xcode-7.0/Swift-2.0 we provide a minimal changes branch where catch and defer are renamed catch_ and defer_ and all other changes are the bare minimum to make PromiseKit 2 compile against Swift 2.

If you still are using Xcode 6 and Swift 1.2 then use PromiseKit 2.

2.0 May 14th, 2015

PromiseKit 2 announcement post.


Swift 1.2 support. Xcode 6.3 required.