// objective-c
// AppDelegate.m
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {

    // after getting user's ID or login
    [SBSMSyncManager setupWithUserId:userId];
}];

// objective-c
- (void)viewDidLoad {    
    SBDGroupChannelListQuery *query = [SBDGroupChannel createMyGroupChannelListQuery];
    // limit, order, ... setup your query here. 
    SBSMChannelCollection *channelCollection = [SBSMChannelCollection collectionWithQuery:query];
    self.channelColletion = channelCollection; // Recommands to set a property of view controller
}

// objective-c
- (void)dealloc {
    if (channelCollection != nil) {
        channelCollection.delegate = nil;
    }
    
    [channelCollection remove];
}

// objective-c

// add delegate
#import <SendBirdSyncManager/SendBirdSyncManager.h>
@interface GroupChannelListViewController : UIViewController <UITableViewDelegate, UITableViewDataSource, SBSMChannelCollectionDelegate>
@end

@implementation GroupChannelListViewController
- (void)viewDidLoad {    
    channelCollection.delegate = self;
    // ..
}

// channel collection delegate
- (void)collection:(SBSMChannelCollection *)collection didReceiveEvent:(SBSMChannelEventAction)action channels:(NSArray<SBDGroupChannel *> *)channels {
    guard collection == self.channelCollection, channels.count > 0 else {
        return
    }

    switch (action) {
        case SBSMChannelEventActionInsert: {
            // Insert channels on list
            break;
        }
        case SBSMChannelEventActionUpdate: {
            // Update channels of list
            break;
        }
        case SBSMChannelEventActionRemove: {
            // Remove channels of list
            break;
        }
        case SBSMChannelEventActionMove: {
            // Move channel of list
            break;
        }
        case SBSMChannelEventActionClear: {
            // Clear(Remove all) channels
            break;
        }
        case SBSMChannelEventActionNone:
        default: {
            break;
        }
    }
}

// objective-c
- (void)viewDidLoad {    
    [channelCollection fetchWithCompletionHandler:^(SBDError * _Nullable error) {
        // This callback is optional and useful to catch the moment of loading ended.
    }];
}

- (void)refreshChannel {
    // begin loading progress
    [channelCollection remove];
    channelCollection = nil;
    // create channel collection 
    [channelCollection fetchWithCompletionHandler:^(SBDError * _Nullable error) {
        // end loading progress
    }];
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    // .. dequeue reusable cell

    if (self.channels.count > 0 && indexPath.row + 1 == self.channels.count) {
        // start loading progress
        [self.channelCollection fetchWithCompletionHandler:^(SBDError * _Nullable error) {
            // end loading progress
        }];
    }

    // ...
}    

// objective-c
- (void)viewDidLoad {
    // ...
    SBSMMessageFilter *filter = [SBSMMessageFilter filterWithMessageType:SBDMessageTypeFilter customType:customtypeFilter senderUserIds:senderUserIdsFilter];
    long long viewpointTimestamp = getLastReadTimestamp();
    // or LONG_LONG_MAX if you want to see the most recent messages

    SBSMMessageCollection *messageCollection = [SBSMMessageCollection collectionWithChannel:self.channel filter:filter viewpointTimestamp:viewpointTimestamp];
    // ...
}

- (void)dealloc {
    if (self.messageCollection != nil) {
        self.messageCollection.delegate = nil;
    }

    [messageCollection remove];
}

// objective-c

// add delegate
#import <SendBirdSyncManager/SendBirdSyncManager.h>
@interface GroupChannelChattingViewController : UIViewController <UITableViewDelegate, UITableViewDataSource, SBSMMessageCollectionDelegate, SBDConnectionDelegate>
@end

@implementation GroupChannelChattingViewController
- (void)viewDidLoad {
    // ..
    messageCollection.delegate = self;
    // ..
}

// message collection delegate
- (void)collection:(SBSMMessageCollection *)collection didReceiveEvent:(SBSMMessageEventAction)action messages:(NSArray<SBDBaseMessage *> *)messages {
    if (self.messageCollection != collection || messages.count == 0) {
        return;
    }

    switch (action) {
        case SBSMMessageEventActionInsert: {
            //
            break;
        }
        case SBSMMessageEventActionUpdate : {
            //
            break;
        }
        case SBSMMessageEventActionRemove: {
            //
            break;
        }
        case SBSMMessageEventActionClear: {
            //
            break;
        }
        case SBSMMessageEventActionNone:
        default:
            break;
    }
}

// objective-c
- (void)viewDidLoad {
    // ..
    [messageCollection fetchInDirection:SBSMMessageDirectionPrevious completionHandler:^(SBDError * _Nullable error) {
        // Fetching from cache is done
    }];
    [messageCollection fetchInDirection:SBSMMessageDirectionNext completionHandler:^(SBDError * _Nullable error) {
        // Fetching from cache is done
    }];
    // ..
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    // .. dequeue reusable cell

    if (self.messages.count > 0 && indexPath.row + 1 == self.messages.count) {
        [messageCollection fetchInDirection:direction completionHandler:^(SBDError * _Nullable error) {
            // fetching from cache is done
        }];
    }

    // ...
}

- (void)refreshMessages {
    [messageCollection resetViewpointTimestamp:getLastReadTimestamp()];
    [messageCollection fetchInDirection:direction completionHandler:^(SBDError * _Nullable error) {
        // Fetching from cache is done
    }];
}

#pragma mark - SendBird Connection Delegate
- (void)didSucceedReconnection {
    [messageCollection resetViewpointTimestamp:getLastReadTimestamp()];
    [messageCollection fetchInDirection:direction completionHandler:^(SBDError * _Nullable error) {
        // Fetching from cache is done
    }];
}

// objective-c 

// call [collection appendMessage:] after sending message
__block SBDUserMessage *previewMessage = [channel sendUserMessageWithParams:params completionHandler:^(SBDUserMessage * _Nullable userMessage, SBDError * _Nullable error) {
    if (error != nil) {
        [messageCollection deleteMessage:previewMessage];
        return;
    }
    
    [self.messageCollection appendMessage:userMessage];
}];

if (previewMessage.requestId != nil) {
    [messageCollection appendMessage:previewMessage];
}


// call [collection updateMessage:] after updating message
[channel sendUserMessageWithParams:params completionHandler:^(SBDUserMessage * _Nullable userMessage, SBDError * _Nullable error) {    
    [self.messageCollection updateMessage:userMessage];
}];

// objective-c
SBSMSyncManager *manager = [SBSMSyncManager manager];
[manager resumeSynchronize];

SBSMSyncManager *manager = [SBSMSyncManager manager];
[manager pauseSynchronize];

// objective-c

// Request Connect to Sendbird
[SBDMain connectWithUserId:userId completionHandler:^(SBDUser * _Nullable user, SBDError * _Nullable error) {
    if (error != nil) {
        // 
        return;
    }
    
    SBSMSyncManager *manager = [SBSMSyncManager manager];
    [manager resumeSynchronize];
}];

// Sendbird Connection Delegate
- (void)didSucceedReconnection {
    SBSMSyncManager *manager = [SBSMSyncManager manager];
    [manager resumeSynchronize];
}

// objective-c
[SBDMain disconnectWithCompletionHandler:^{

    // clear cache
    [[SBSMSyncManager manager] clearCache];

    // stop synchronizing
    [[SBSMSyncManager manager] pauseSynchronize];
}];