Alley

Essential

URLSessionDataTask

Why

In most cases where you need to fetch something from the internet, you:

1. Want to get the data at the URL you are targeting, no matter what
2. In case when it’s simply not possible, display some useful error to the end-customer and display / log what error actually happened so you can troubleshoot and debug

Second point is nice to have. First one is vastly more important since that data is the reason you are doing this at all.

Thus main feature of Alley is automatic request retries for predefined conditions.

Integration

Manually

Just drag

Alley

If you prefer to use dependency managers, see below. Releases are tagged with Semantic Versioning in mind.

Swift Package Manager

Ready, just add this repo URL as Package. I recommend to link with

master

CocoaPods

CocoaPods is a dependency manager for Cocoa projects. For usage and installation instructions, visit their website. To integrate Alley into your Xcode project using CocoaPods, specify it in your

Podfile

pod 'Alley',    :git => 'https://github.com/radianttap/Alley.git'

Setting up with Carthage

Carthage is a decentralized dependency manager that automates the process of adding frameworks to your Cocoa application.

You can install Carthage with Homebrew using the following command:

$ brew update
$ brew install carthage

To integrate Alley into your Xcode project using Carthage, specify it in your

Cartfile

github "radianttap/Alley"

Usage

You would already have some

URLSession

let urlRequest = URLRequest(...)

urlSession.dataTask(with: urlRequest) {
    data, urlResponse, error in
    //...process error, response, data
}
task.resume()

with Alley you will do this:

let urlRequest = URLRequest(...)

urlSession.performNetworkRequest(urlRequest) {
    networkResult in
    //...process networkResult
}

That’s the basic change, now let’s see what is this

NetworkResult

NetworkResult

This is your standard Swift’s Result type, defined like this:

typealias NetworkResult = Result

In case the request was successful, you would get the

Data

In case of failure, you get an instance of

NetworkError

NetworkError

This is custom Error (implemented by an enum) which – for starters – wraps stuff returned by

URLSessionDataTask

/// `URLSession` errors are passed-through, handle as appropriate.
case urlError(URLError)

/// URLSession returned an Error object which is not URLError
case generalError(Swift.Error)

Then it handles the least possible scenario to happen: no error returned by

URLSessionDataTask

URLResponse

case noResponse

Next, if the returned

URLResponse

HTTPURLResponse

case invalidResponseType(URLResponse)

Now, if it is

HTTPURLResponse

400

HTTPURLResponse

Data

case endpointError(HTTPURLResponse, Data?)

In the calling object, you can use these values and try to build instances of strongly-typed custom errors related to the given specific web service.

If status code is in

2xx

case noResponseData(HTTPURLResponse)

This may or may not be an error. If you perform

PUT

DELETE

POST

200 OK

let urlRequest = URLRequest(...)

urlSession.performNetworkRequest(urlRequest, allowEmptyData: true) {
    networkResult in
    //...process networkResult
}

where you will get empty

Data()

DataResult.success

There’s one more possible

NetworkError

Automatic retries

Default number of retries is

10

This value is automatically used for all

perform()

maxRetries

let urlRequest = URLRequest(...)

urlSession.performNetworkRequest(urlRequest, maxRetries: 5) {
    networkResult in
    //...process networkResult
}

How automatic retries work?

In case of a

NetworkError

shouldRetry

true

URLSessionDataTask

maxRetries

NetworkError.inaccessible

There is currently no delay between retries, it simply tries again.

You can customize the behavior by changing the implementation of

shouldRetry

NetworkError.urlError

true

URLError

That’s about it. Alley is intentionally simple to encourage writing as little code as possible, hiding away often-repeated boilerplate.

License

MIT License, like all my open source code.

Give back

If you found this code useful, please consider buying me a coffee or two. ☕️😋