fucntional methods for array

MVMCore/MVMCore/Categories/NSArray+MFConvenience.h

@@ -38,6 +38,9 @@
 - (nonnull NSString *)stringAtIndex:(NSUInteger)index;
 
 // Maps this array to a new array of T objects given a conversion block. Objective-C implementation of Swift's map. https://developer.apple.com/documentation/swift/array/2908681-map
-- (nonnull NSArray *) map:(id _Nullable (^_Nonnull)(id _Nonnull obj))mapBlock;
+- (nonnull NSArray *)map:(id _Nullable (^_Nonnull)(id _Nonnull obj))mapBlock;
+- (nonnull NSArray *)filter:(BOOL (^_Nullable)(id _Nonnull obj))block;
+- (nonnull id)reduce:(nonnull id)initial block:(id (^_Nullable)(id _Nonnull obj1, id obj2))block;
+- (NSArray *_Nullable)flatMap:(id (^_Nonnull)(id obj))block;
 
 @end

MVMCore/MVMCore/Categories/NSArray+MFConvenience.m

@@ -96,4 +96,36 @@
     return mapped;
 }
 
+- (NSArray *)filter:(BOOL (^)(id obj))block {
+    NSMutableArray *mutableArray = [NSMutableArray new];
+    [self enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
+        if (block(obj) == YES) {
+            [mutableArray addObject:obj];
+        }
+    }];
+    return mutableArray;
+}
+
+- (id)reduce:(id)initial block:(id (^)(id obj1, id obj2))block {
+    __block id obj = initial;
+    [self enumerateObjectsUsingBlock:^(id _obj, NSUInteger idx, BOOL *stop) {
+        obj = block(obj, _obj);
+    }];
+    return obj;
+}
+
+- (NSArray *)flatMap:(id (^)(id obj))block {
+    NSMutableArray *mutableArray = [NSMutableArray new];
+    [self enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
+        id _obj = block(obj);
+        if ([_obj isKindOfClass:[NSArray class]]) {
+            NSArray *_array = [_obj flatMap:block];
+            [mutableArray addObjectsFromArray:_array];
+            return;
+        }
+        [mutableArray addObject:_obj];
+    }];
+    return mutableArray;
+}
+
 @end