Support using flags with options

Author: kylef

Commander/ArgumentDescription.swift

@@ -57,13 +57,15 @@ public class Option<T : ArgumentConvertible> : ArgumentDescriptor {
   public typealias Validator = ValueType throws -> ValueType
 
   public let name:String
+  public let flag:Character?
   public let description:String?
   public let `default`:ValueType
   public var type:ArgumentType { return .Option }
   public let validator:Validator?
 
-  public init(_ name:String, _ `default`:ValueType, description:String? = nil, validator: Validator? = nil) {
+  public init(_ name:String, _ `default`:ValueType, flag:Character? = nil, description:String? = nil, validator: Validator? = nil) {
     self.name = name
+    self.flag = flag
     self.description = description
     self.`default` = `default`
     self.validator = validator
@@ -80,6 +82,18 @@ public class Option<T : ArgumentConvertible> : ArgumentDescriptor {
       return value
     }
 
+    if let flag = flag {
+      if let value = try parser.shiftValueForFlag(flag) {
+        let value = try T(string: value)
+
+        if let validator = validator {
+          return try validator(value)
+        }
+
+        return value
+      }
+    }
+
     return `default`
   }
 }

Commander/ArgumentParser.swift

@@ -164,4 +164,52 @@ public final class ArgumentParser : ArgumentConvertible, CustomStringConvertible
 
     return false
   }
+
+  /// Returns the value for a flag (-n Kyle)
+  public func shiftValueForFlag(flag:Character) throws -> String? {
+    return try shiftValuesForFlag(flag)?.first
+  }
+
+  /// Returns the value for a flag (-n Kyle)
+  public func shiftValuesForFlag(flag:Character, count:Int = 1) throws -> [String]? {
+    var index = 0
+    var hasFlag = false
+
+    for argument in arguments {
+      switch argument {
+      case .Flag(let flags):
+        if flags.contains(flag) {
+          hasFlag = true
+          break
+        }
+        fallthrough
+      default:
+        ++index
+      }
+
+      if hasFlag {
+        break
+      }
+    }
+
+    if hasFlag {
+      ++index // Jump flags
+
+      return try (0..<count).map { i in
+        if arguments.count > index {
+          let argument = arguments.removeAtIndex(index)
+          switch argument {
+          case .Argument(let value):
+            return value
+          default:
+            throw ArgumentParserError(description: "Unexpected \(argument.type) `\(argument)` as a value for `-\(flag)`")
+          }
+        }
+
+        throw ArgumentParserError(description: "Missing value for `-\(flag)`")
+      }
+    }
+    
+    return nil
+  }
 }