Objective-C ArrayMapper

Objective-C_ArrayMapper.m

#import <Foundation/Foundation.h>

@interface ArrayMapper <InputType, OutputType> : NSObject

- (nonnull NSArray <OutputType> *)map:(nonnull NSArray <InputType> *)inputArray withBlock:(nonnull OutputType _Nonnull (^)(InputType _Nonnull obj))block;
- (nonnull NSArray <OutputType> *)flatMap:(nonnull NSArray <InputType> *)inputArray withBlock:(nonnull OutputType _Nullable (^)(InputType _Nonnull obj))block;

@end

@implementation ArrayMapper

- (nonnull NSArray *)map:(nonnull NSArray *)inputArray withBlock:(nonnull id  _Nonnull (^)(id _Nonnull))block
{
    NSMutableArray *outputArray = [[NSMutableArray alloc] initWithCapacity:inputArray.count];
    [inputArray enumerateObjectsUsingBlock:^(id inputObject, NSUInteger idx, BOOL *stop) {
        [outputArray addObject:block(inputObject)];
    }];

    return [outputArray copy];
}

- (nonnull NSArray *)flatMap:(nonnull NSArray *)inputArray withBlock:(nonnull id  _Nullable (^)(id _Nonnull))block
{
    NSMutableArray *outputArray = [NSMutableArray new];
    [inputArray enumerateObjectsUsingBlock:^(id inputObject, NSUInteger idx, BOOL *stop) {
        id outputObject = block(inputObject);
        if (outputObject) [outputArray addObject:outputObject];
    }];

    return [outputArray copy];
}

@end