Add title formatter to support selection styling

Author: leontiy

HMSegmentedControl/HMSegmentedControl.h

@@ -8,7 +8,10 @@
 
 #import <UIKit/UIKit.h>
 
+@class HMSegmentedControl;
+
 typedef void (^IndexChangeBlock)(NSInteger index);
+typedef NSAttributedString *(^HMTitleFormatterBlock)(HMSegmentedControl *segmentedControl, NSString *title, BOOL selected);
 
 typedef enum {
     HMSegmentedControlSelectionStyleTextWidthStripe, // Indicator width will only be as big as the text width
@@ -40,6 +43,9 @@ typedef enum {
 
 @interface HMSegmentedControl : UIControl
 
+/* 
+ * Array of `NSString` objects
+ */
 @property (nonatomic, strong) NSArray *sectionTitles;
 @property (nonatomic, strong) NSArray *sectionImages;
 @property (nonatomic, strong) NSArray *sectionSelectedImages;
@@ -51,6 +57,13 @@ typedef enum {
  */
 @property (nonatomic, copy) IndexChangeBlock indexChangeBlock;
 
+/*
+ * This block is used to apply custom text styling to titles when set.
+ *
+ * When this block is provided, no additional styling is applied to the `NSAttributedString` object returned from this block.
+ */
+@property (nonatomic, copy) HMTitleFormatterBlock titleFormatter;
+
 /*
  Text attributes to apply to item title texts.
  

HMSegmentedControl/HMSegmentedControl.m

@@ -219,15 +219,13 @@ - (CGSize)measureTitleAtIndex:(NSUInteger)idx {
 }
 
 - (NSAttributedString *)attributedTitleAtIndex:(NSUInteger)idx {
-    id title = self.sectionTitles[idx];
-    if ([title isKindOfClass:[NSString class]]) {
-        NSDictionary *titleAttrs = idx == self.selectedSegmentIndex ? [self resultingSelectedTitleTextAttributes] : [self resultingTitleTextAttributes];
+    NSString *title = self.sectionTitles[idx];
+    BOOL selected = idx == self.selectedSegmentIndex;
+    if (self.titleFormatter == nil) {
+        NSDictionary *titleAttrs = selected ? [self resultingSelectedTitleTextAttributes] : [self resultingTitleTextAttributes];
         return [[NSAttributedString alloc] initWithString:(NSString *)title attributes:titleAttrs];
-    } else if ([title isKindOfClass:[NSAttributedString class]]) {
-        return (NSAttributedString *)title;
     } else {
-        NSAssert(title == nil, @"Unexpected type of segment title: %@", [title class]);
-        return nil;
+        return self.titleFormatter(self, title, selected);
     }
 }