Functional methods for NSArray

NSArray+SFBFunctional.h

//
// Copyright (c) 2020 - 2021 Stephen F. Booth <me@sbooth.org>
// MIT license
//

#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

@interface NSArray<ObjectType> (SFBFunctional)
/// Returns an array containing the results of applying \c block to each element in \c self
- (NSArray *)mappedArrayUsingBlock:(id (^)(ObjectType obj))block;
/// Returns a copy of \c self including only elements for which \c block returns \c YES
- (NSArray<ObjectType> *)filteredArrayUsingBlock:(BOOL (^)(ObjectType obj))block;
@end

NS_ASSUME_NONNULL_END

NSArray+SFBFunctional.m

//
// Copyright (c) 2020 - 2021 Stephen F. Booth <me@sbooth.org>
// MIT license
//

#import "NSArray+SFBFunctional.h"

@implementation NSArray (SFBFunctional)

- (NSArray *)mappedArrayUsingBlock:(id (^)(id))block
{
	NSParameterAssert(block != NULL);
	
	NSMutableArray *result = [NSMutableArray arrayWithCapacity:self.count];
	for(id obj in self) {
		id newobj = block(obj);
		[result addObject:(newobj ?: [NSNull null])];
	}
	return result;
}

- (NSArray *)filteredArrayUsingBlock:(BOOL (^)(id))block
{
	NSParameterAssert(block != NULL);

	return [self objectsAtIndexes:[self indexesOfObjectsPassingTest:^BOOL(id obj, NSUInteger idx, BOOL *stop) {
#pragma unused(idx)
#pragma unused(stop)
		return block(obj);
	}]];
}

@end