Add vertical anchors

Source/UIScrollView+EmptyDataSet.h

@@ -12,9 +12,16 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
+typedef NS_ENUM (NSUInteger, DZNEmptyDataSetVerticalAnchorLocation) {
+    DZNEmptyDataSetVerticalAnchorLocationCenter = 0,
+    DZNEmptyDataSetVerticalAnchorLocationTop,
+    DZNEmptyDataSetVerticalAnchorLocationBottom
+};
+
 @protocol DZNEmptyDataSetSource;
 @protocol DZNEmptyDataSetDelegate;
 
+
 #define DZNEmptyDataSetDeprecated(instead) DEPRECATED_MSG_ATTRIBUTE(" Use " # instead " instead")
 
 /**
@@ -155,6 +162,14 @@ NS_ASSUME_NONNULL_BEGIN
  */
 - (CGFloat)spaceHeightForEmptyDataSet:(UIScrollView *)scrollView;
 
+/**
+ Asks the data source for a vertical anchor location. Default is DZNEmptyDataSetVerticalAnchorLocationCenter.
+
+ @param scrollView A scrollview subclass object informing the data source.
+ @return A DZNEmptyDataSetVerticalAnchorLocation value indicating if the view should be pinned to the top, center, or bottom of its container.
+ */
+- (DZNEmptyDataSetVerticalAnchorLocation)verticalAnchorLocationForEmptyDataSet:(UIScrollView *)scrollView;
+
 @end
 
 

Source/UIScrollView+EmptyDataSet.m

@@ -37,6 +37,7 @@ @interface DZNEmptyDataSetView : UIView
 
 @property (nonatomic, assign) CGFloat verticalOffset;
 @property (nonatomic, assign) CGFloat verticalSpace;
+@property (nonatomic, assign) DZNEmptyDataSetVerticalAnchorLocation verticalAnchorLocation;
 
 @property (nonatomic, assign) BOOL fadeInOnDisplay;
 
@@ -283,6 +284,15 @@ - (CGFloat)dzn_verticalSpace
     return 0.0;
 }
 
+- (DZNEmptyDataSetVerticalAnchorLocation)dzn_verticalAnchorLocation
+{
+    if (self.emptyDataSetSource && [self.emptyDataSetSource respondsToSelector:@selector(verticalAnchorLocationForEmptyDataSet:)]) {
+        return [self.emptyDataSetSource verticalAnchorLocationForEmptyDataSet:self];
+    }
+
+    return DZNEmptyDataSetVerticalAnchorLocationCenter;
+}
+
 
 #pragma mark - Delegate Getters & Events (Private)
 
@@ -522,6 +532,9 @@ - (void)dzn_reloadEmptyDataSet
         // Configure offset
         view.verticalOffset = [self dzn_verticalOffset];
 
+        // Configure anchor location
+        view.verticalAnchorLocation = [self dzn_verticalAnchorLocation];
+
         // Configure the empty dataset view
         view.backgroundColor = [self dzn_dataSetBackgroundColor];
         view.hidden = NO;
@@ -921,15 +934,30 @@ - (void)setupConstraints
     // First, configure the content view constaints
     // The content view must alway be centered to its superview
     NSLayoutConstraint *centerXConstraint = [self equallyRelatedConstraintWithView:self.contentView attribute:NSLayoutAttributeCenterX];
-    NSLayoutConstraint *centerYConstraint = [self equallyRelatedConstraintWithView:self.contentView attribute:NSLayoutAttributeCenterY];
+    NSLayoutConstraint *verticalAnchorConstraint = nil;
+
+    switch (self.verticalAnchorLocation) {
+        case DZNEmptyDataSetVerticalAnchorLocationCenter: {
+            verticalAnchorConstraint = [self equallyRelatedConstraintWithView:self.contentView attribute:NSLayoutAttributeCenterY];
+            break;
+        }
+        case DZNEmptyDataSetVerticalAnchorLocationTop: {
+            verticalAnchorConstraint = [self equallyRelatedConstraintWithView:self.contentView attribute:NSLayoutAttributeTop];
+            break;
+        }
+        case DZNEmptyDataSetVerticalAnchorLocationBottom: {
+            verticalAnchorConstraint = [self equallyRelatedConstraintWithView:self.contentView attribute:NSLayoutAttributeBottom];
+            break;
+        }
+    }
 
     [self addConstraint:centerXConstraint];
-    [self addConstraint:centerYConstraint];
+    [self addConstraint:verticalAnchorConstraint];
     [self addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[contentView]|" options:0 metrics:nil views:@{@"contentView": self.contentView}]];
 
     // When a custom offset is available, we adjust the vertical constraints' constants
     if (self.verticalOffset != 0 && self.constraints.count > 0) {
-        centerYConstraint.constant = self.verticalOffset;
+        verticalAnchorConstraint.constant = self.verticalOffset;
     }
 
     // If applicable, set the custom view's constraints