optimize selected

TZImagePickerController/TZImagePickerController/TZAssetModel.m

@@ -52,7 +52,7 @@
 
 - (void)checkSelectedModels {
     self.selectedCount = 0;
-    NSMutableArray *selectedAssets = [NSMutableArray array];
+    NSMutableSet *selectedAssets = [NSMutableSet setWithCapacity:_selectedModels.count];
     for (TZAssetModel *model in _selectedModels) {
         [selectedAssets addObject:model.asset];
     }

TZImagePickerController/TZImagePickerController/TZPhotoPickerController.m

@@ -781,9 +781,10 @@ static CGFloat itemMargin = 5;
 }
 
 - (void)checkSelectedModels {
-    NSMutableArray *selectedAssets = [NSMutableArray array];
     TZImagePickerController *tzImagePickerVc = (TZImagePickerController *)self.navigationController;
-    for (TZAssetModel *model in tzImagePickerVc.selectedModels) {
+    NSArray *selectedModels = tzImagePickerVc.selectedModels;
+    NSMutableSet *selectedAssets = [NSMutableSet setWithCapacity:selectedModels.count];
+    for (TZAssetModel *model in selectedModels) {
         [selectedAssets addObject:model.asset];
     }
     for (TZAssetModel *model in _models) {