Add options

lib/motion-layout/layout.rb

@@ -21,28 +21,54 @@ def view(view)
       @view = view
     end
 
-    def horizontal(horizontal)
-      @horizontals << horizontal
+    def horizontal(horizontal, *options)
+      options = [:centery] if options.empty?
+      @horizontals << [horizontal, resolve_options(options)]
     end
 
-    def vertical(vertical)
-      @verticals << vertical
+    def vertical(vertical, *options)
+      options = [:centerx] if options.empty?
+      @verticals << [vertical, resolve_options(options)]
     end
 
     private
 
+    def resolve_options(opt)
+      opt_hash = {
+        left: NSLayoutFormatAlignAllLeft,
+        right: NSLayoutFormatAlignAllRight,
+        top: NSLayoutFormatAlignAllTop,
+        bottom: NSLayoutFormatAlignAllBottom,
+        leading: NSLayoutFormatAlignAllLeading,
+        trailing: NSLayoutFormatAlignAllTrailing,
+        centerx: NSLayoutFormatAlignAllCenterX,
+        centery: NSLayoutFormatAlignAllCenterY,
+        baseline: NSLayoutFormatAlignAllBaseline,
+      }
+      opt.inject(0) do |m,x|
+        if x.kind_of?(Numeric)
+          m | x.to_i
+        elsif o = opt_hash[x.to_s.downcase.to_sym]
+          m | o
+        else
+          raise "invalid opt: #{x.to_s.downcase}"
+        end
+      end
+    end
+
     def strain
       @subviews.values.each do |subview|
+        next if @view == subview # you wouldn't believe the mess it would create
         subview.translatesAutoresizingMaskIntoConstraints = false
         @view.addSubview(subview)
       end
 
       constraints = []
-      constraints += @verticals.map do |vertical|
-        NSLayoutConstraint.constraintsWithVisualFormat("V:#{vertical}", options:NSLayoutFormatAlignAllCenterX, metrics:@metrics, views:@subviews)
+      constraints += @verticals.map do |vertical, options|
+        NSLayoutConstraint.constraintsWithVisualFormat("V:#{vertical}", options:options, metrics:@metrics, views:@subviews)
       end
-      constraints += @horizontals.map do |horizontal|
-        NSLayoutConstraint.constraintsWithVisualFormat("H:#{horizontal}", options:NSLayoutFormatAlignAllCenterY, metrics:@metrics, views:@subviews)
+      constraints += @horizontals.map do |horizontal, options|
+        NSLayoutConstraint.constraintsWithVisualFormat("H:#{horizontal}", options:options, metrics:@metrics, views:@subviews)
       end
 
       @view.addConstraints(constraints.flatten)