Add conversion documentation for env.ts

Author: MasterJ93

Conversion Documentation/common env conversion.md

@@ -0,0 +1,40 @@
+# Conversion for `env.ts`
+
+## `export const envInt = (name: string): number | undefined` 
+
+This is redundant and will not be converted. Simply use `ProcessInfo` and wrap it into an `Int` initializer. A fallback can be made by using `??`.
+
+```swift
+let port = Int(ProcessInfo.processInfo.environment["PORT"] ?? "") ?? 8080
+```
+
+## `export const envStr = (name: string): string | undefined`
+
+This is redundant and will not be converted. Simply use `ProcessInfo` and wrap it into a `String` initializer. A fallback can be made by using `??`.
+
+```swift
+let nameValue = String(ProcessInfo.processInfo.environment["NAME"] ?? "")
+```
+
+## `export const envBool = (name: string): boolean | undefined`
+
+This is redunant and will not be converted. Simply use `ProcessInfo` for this. Creating a method for this is trivial:
+
+```swift
+func envBool(_ name: String) -> Bool? {
+    guard let value = ProcessInfo.processInfo.environment[name]?.lowercased() else { return nil }
+    switch value {
+        case "true", "1": return true
+        case "false", "0": return false
+        default: return nil
+    }
+}
+```
+
+## `export const envList = (name: string): string[]`
+
+This is redundant and will not be converted. Simply use `ProcessInfo` for this. This can be done with just one line:
+
+```swift
+let arrayItems = ProcessInfo.processInfo.environment["ITEMS"]?.split(separator: ",").map(String.init) ?? []
+```