Category Archives: Swift

AppDeveloperKit-String: A Swift library for subscripting, regular expression matching and substitutions

String shortcomings

I really enjoy programming in Swift, but I’ve always been bothered a bit by what I perceived as a couple of shortcomings related to the String class.


There is no support for subscripting a String.

Try the following in a Playground and you’ll get an error:

 let str = "Hello"

 str[1]   // 'subscript' is unavailable: cannot subscript String with an Int
 str[1..<3] // 'subscript' is unavailable: cannot subscript String with an integer range

You can find a mention of this restriction in some source code comments.

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Solving a HackerRank algorithm problem – Matrix Layer Rotation

Matrix Layer Rotation

I enjoy solving interesting HackerRank algorithm problems.  I came across one recently called Matrix Layer Rotation – appropriately labeled “hard” by the author.

I posted my solution as a playground on GitHub.

The problem is to print out a rotated representation of a m x n  matrix given the parameters:

m – number of rows
n – number of columns
r – number of rotations

Looking at the constraints

2 <= m, n <= 300
1 <= r <= 10^^9
min(m,n) % 2 = 0

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Leave Swift Error Propagation Enabled

A harmless Database update

I was debugging a Swift Mac app that I’m developing that uses Realm for a database.  The version of RealmSwift I was currently using was 2.10.0 as specified in my Podfile.

I opened Realm Browser to inspect a record in my database.   Having been recently updated to version 3.0.1, it alerted me that my database was using an older file format and offered to upgrade it.   I accepted without thinking much of it.

An unexpected error

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Error reporting for complex unit tests

System level unit testing

I was recently putting together the structure for some system level unit tests of a Swift project.   The structure extended beyond a single file for these tests.   I currently have:

  • SystemTests – Base class for a suite of system level unit tests.
  • BasicSystemTests – Class for my first group of unit tests.  Derives from SystemTests.
  • Various utility classes, each specific to a major section of the project.

Here is an example chain of calls coming from a test case:


   func testModified () {
        // Test modification to Project
        createProject(name: "Test Project", bundleId: "TestBundleId", appDelegate: "TestAppDelegate", fsConfig: "TestFsConfig", description: "Test Project Description")


   func createProject(name: String, bundleId: String, appDelegate: String?, fsConfig: String?, description: String?) -> String? {
        // Is Add New button enabled?
        project.verifyAddNewButton(enabled: false)


    func verifyAddNewButton(enabled: Bool) {
        XCTAssertEqual(addNewButton.isEnabled, enabled, "Add New button enabled = \(enabled)")

The problem – what is the path?

My test case has a bug.  When I run the test case, I see the following in Issue Navigator and the source code editor:

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Swift framework development for binary distribution with CocoaPods

Swift Framework with Objective-C

Having previously developed some Objective-C based frameworks, I set out to explore doing the same with Swift and be able to deliver the framework as a Pod.

Creating a a Swift Framework is pretty straightforward and there are some great references on the subject.  One that I found very helpful was Creating and Distributing iOS Frameworks

I wanted to include some Objective-C based CocoaPods in my Swift Framework and quickly ran into an issue – you can’t use bridging headers with framework targets.

I did find a workaround which was interesting.  An answer in the thread Importing CommonCrypto in a Swift framework showed how to create a module that could be imported into Swift using an Aggregate target.  Using this answer as a guide, I was able to create a module for AFNetworking using the run script:

mkdir -p "${BUILT_PRODUCTS_DIR}/AFNetworkingModuleMap"
cat <<EOF > "${BUILT_PRODUCTS_DIR}/AFNetworkingModuleMap/module.modulemap"
module AFNetworking [system] {
header "${PODS_ROOT}/Headers/Public/AFNetworking/AFNetworking.h"
export *

This was interesting, but not the right approach.

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