Enforced initialOpenSections and sectionsAlwaysOpen to be set at the start.

Author: kgaidis

FZAccordionTableView/FZAccordionTableView.h

@@ -69,13 +69,17 @@
 /*!
  @desc  Defines which sections should be open the first time the
         table is shown.
+ 
+        Must be set before any data is loaded.
  */
 @property (strong, nonatomic, nullable) NSSet <NSNumber *> *initialOpenSections;
 
 /*!
  @desc  Defines which sections will always be open.
         The headers of these sections will not call the
         FZAccordionTableViewDelegate methods.
+ 
+        Must be set before any data is loaded.
  */
 @property (strong, nonatomic, nullable) NSSet <NSNumber *> *sectionsAlwaysOpen;
 

FZAccordionTableView/FZAccordionTableView.m

@@ -256,10 +256,16 @@ - (BOOL)respondsToSelector:(SEL)aSelector {
 #pragma mark - Override Setters -
 
 - (void)setInitialOpenSections:(NSSet *)initialOpenedSections {
+    NSAssert(self.sectionInfos.count == 0, @"'initialOpenedSections' MUST be set before the tableView has started loading data.");
     _initialOpenSections = initialOpenedSections;
     _mutableInitialOpenSections = [initialOpenedSections mutableCopy];
 }
 
+- (void)setSectionsAlwaysOpen:(NSSet<NSNumber *> *)sectionsAlwaysOpen {
+    NSAssert(self.sectionInfos.count == 0, @"'sectionsAlwaysOpen' MUST be set before the tableView has started loading data.");
+    _sectionsAlwaysOpen = sectionsAlwaysOpen;
+}
+
 #pragma mark - FZAccordionTableViewHeaderViewDelegate -
 
 - (void)tappedHeaderView:(FZAccordionTableViewHeaderView *)sectionHeaderView {