Detect unused code – Periphery

Codebases are growing over time (most of the times). They do also go after minor or major refactors. And regardless how careful or not is the team, there are often cases that there is some unused code left in the codebase.
In this article we will use the Periphery(https://github.com/peripheryapp/periphery) tool to detect unused code.

1. Let’s create a project and name it UnusedCodeTest.
2. Install through brew the periphery
   Swift

   brew install peripheryapp/periphery/periphery

   1	brew install peripheryapp/periphery/periphery

3. Next let’s add an unused class in the target:
   Swift

   class UnusedClass { }

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   class UnusedClass {      }

4. Also we add an unused method, a used method and a used method with an unused parameter:
   Swift

   struct ContentView: View { var body: some View { VStack { Text("Hello, world!") .padding() } .onAppear(perform: { methodCalled() methodUnusedParameter(a: 3, b: 4) }) } func methodCalled() { } func methodUnCalled() { } func methodUnusedParameter(a: Int, b: Int) { _ = a * a } }

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   struct ContentView: View {     var body: some View {         VStack {             Text("Hello, world!")                 .padding()         }         .onAppear(perform: {             methodCalled()             methodUnusedParameter(a: 3, b: 4)         })     }          func methodCalled() {              }          func methodUnCalled() {              }          func methodUnusedParameter(a: Int, b: Int) {         _ = a * a     } }

5. Now let’s run the command:
   Swift

   periphery scan --setup

   1	periphery scan --setup

   And this will guide us through the setup:
   

6. As a result we have a yml file with these details
   
   Swift

   project: UnusedCodeTest.xcodeproj schemes: - UnusedCodeTest targets: - UnusedCodeTest

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   project: UnusedCodeTest.xcodeproj schemes: - UnusedCodeTest targets: - UnusedCodeTest

7. Now let’s see how good is the tool:
   
   It found 3 out 3 issues! Not bad at all!