ThreadSafeMutableArray.h

//
// Created on 2019/1/25.
//

#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

@interface ThreadSafeMutableArray<ObjectType> : NSObject <NSFastEnumeration, NSCopying>

+ (instancetype)array;

- (void)addObject:(ObjectType)obj;
- (void)removeAllObjects;

@end

NS_ASSUME_NONNULL_END

ThreadSafeMutableArray.m

//
// Created on 2019/1/25.
//

#import "ThreadSafeMutableArray.h"
#import <pthread/pthread.h>

#define WriteLock(x) \
    pthread_rwlock_wrlock(&_rwlock); \
    x; \
    pthread_rwlock_unlock(&_rwlock)

#define ReadLock(x) \
    pthread_rwlock_rdlock(&_rwlock); \
    x; \
    pthread_rwlock_unlock(&_rwlock)

@interface ThreadSafeMutableArray () {
    NSMutableArray *_backedArray;
    pthread_rwlock_t _rwlock;
}

@end

@implementation ThreadSafeMutableArray

+ (instancetype)new
{
    return [[self alloc] init];
}

- (instancetype)init
{
    self = [super init];
    if (self) {
        _backedArray = [NSMutableArray array];
        pthread_rwlock_init(&_rwlock, NULL);
    }
    return self;
}

- (void)dealloc
{
    pthread_rwlock_destroy(&_rwlock);
}

#pragma mark - Public apis

+ (instancetype)array
{
    return [self new];
}

- (void)addObject:(id)obj
{
    if (!obj) {
        return;
    }
    
    WriteLock([_backedArray addObject:obj]);
}

- (void)removeAllObjects
{
    WriteLock({
        [_backedArray removeAllObjects];
    });
}


#pragma mark - NSCopying

- (id)copyWithZone:(NSZone *)zone
{
    return _backedArray.copy;
}

#pragma mark - NSFastEnumeration

- (NSUInteger)countByEnumeratingWithState:(nonnull NSFastEnumerationState *)state objects:(id  _Nullable __unsafe_unretained * _Nonnull)buffer count:(NSUInteger)len {
    ReadLock(NSUInteger count = [_backedArray.copy countByEnumeratingWithState:state objects:buffer count:len]);
    return count;
}

@end