Fix Xcode 9 warnings in ColorPicker source

ColorPicker/ColorPicker/CPKColorWell.h

@@ -13,10 +13,10 @@
 @property(nonatomic, assign) BOOL noColorAllowed;
 // Called just before popover opens.
-@property(nonatomic, copy) void (^willOpenPopover)();
+@property(nonatomic, copy) void (^willOpenPopover)(void);
 // Called just before popover closes.
-@property(nonatomic, copy) void (^willClosePopover)();
+@property(nonatomic, copy) void (^willClosePopover)(void);
 // Override these methods to customize how the popover is presented. Normally it is presented from
 // the color well's frame.

ColorPicker/ColorPicker/CPKColorWell.m

@@ -4,8 +4,8 @@
 #import "NSObject+CPK.h"
 @protocol CPKColorWellViewDelegate
-@property(nonatomic, readonly) void (^willOpenPopover)();
-@property(nonatomic, readonly) void (^willClosePopover)();
+@property(nonatomic, readonly) void (^willOpenPopover)(void);
+@property(nonatomic, readonly) void (^willClosePopover)(void);
 - (NSRect)presentationRect;
 - (NSView *)presentingView;

ColorPicker/ColorPicker/CPKMainViewController.h

@@ -31,7 +31,7 @@ typedef NS_OPTIONS(NSInteger, CPKMainViewControllerOptions) {
                  alphaAllowed:(BOOL)alphaAllowed DEPRECATED_ATTRIBUTE;
 - (instancetype)initWithBlock:(void (^)(NSColor *))block
-         useSystemColorPicker:(void (^)())useSystemColorPickerBlock
+         useSystemColorPicker:(void (^)(void))useSystemColorPickerBlock
                         color:(NSColor *)color
                       options:(CPKMainViewControllerOptions)options;

ColorPicker/ColorPicker/CPKMainViewController.m

@@ -40,7 +40,7 @@ static const CGFloat kBottomMargin = 8;
 }
 - (instancetype)initWithBlock:(void (^)(NSColor *))block
-         useSystemColorPicker:(void (^)())useSystemColorPickerBlock
+         useSystemColorPicker:(void (^)(void))useSystemColorPickerBlock
                         color:(NSColor *)color
                       options:(CPKMainViewControllerOptions)options {
     self = [super initWithNibName:nil bundle:nil];

ColorPicker/ColorPicker/CPKPopover.h

@@ -13,7 +13,7 @@
 @property(nonatomic, strong) NSColor *selectedColor;
 /** Called before popover closes. */
-@property(nonatomic, copy) void (^willClose)();
+@property(nonatomic, copy) void (^willClose)(void);
 /**
  * Shows the color picker in a popover. Returns the semitransient popover.
@@ -39,6 +39,6 @@
                          initialColor:(NSColor *)color
                               options:(CPKMainViewControllerOptions)options
                    selectionDidChange:(void (^)(NSColor *))block
-                 useSystemColorPicker:(void (^)())useSystemColorPicker;
+                 useSystemColorPicker:(void (^)(void))useSystemColorPicker;
 @end

ColorPicker/ColorPicker/CPKPopover.m

@@ -28,7 +28,7 @@
                          initialColor:(NSColor *)color
                          options:(CPKMainViewControllerOptions)options
                    selectionDidChange:(void (^)(NSColor *))block
-                 useSystemColorPicker:(void (^)())useSystemColorPicker {
+                 useSystemColorPicker:(void (^)(void))useSystemColorPicker {
     CPKPopover *popover = [[CPKPopover alloc] init];
     popover.mainViewController = [[CPKMainViewController alloc] initWithBlock:block
                                                          useSystemColorPicker:useSystemColorPicker