Join A Group

Quick Reference for AI Agents & Developers

Join group: CometChat.joinGroup(GUID:groupType:password:onSuccess:onError:)
Public groups: No password required
Password groups: Password required
Private groups: Cannot join directly — must be added by admin/owner
Related: Create Group · Leave Group · Groups Overview

In order to start participating in group conversations, you will have to join a group. You can do so using the joinGroup() method.

Join Group Parameters

Parameter	Type	Description
GUID	String	Unique group identifier
groupType	GroupType	`.public`, `.private`, or `.password`
password	String?	Required for `.password` groups

Group Type Behavior

Type	Can Join Directly	Password Required
.public	Yes	No
.password	Yes	Yes
.private	No	N/A (must be added by admin)

Swift
Objective C

let guid = "cometchat-guid-11"
let password: String? = nil // mandatory in case of password protected group type

CometChat.joinGroup(GUID: guid, groupType: .public, password: nil, onSuccess: { (group) in
    print("Group joined successfully. " + group.stringValue())
}, onError: { (error) in
    print("Group joining failed with error:" + error!.errorDescription)
})

NSString *guid = @"cometchat-guid-101";
NSString *password = nil; // mandatory in case of password protected group type

[CometChat joinGroupWithGUID:guid groupType:groupTypePublic password:password onSuccess:^(Group * group) {
    NSLog(@"Group joined successfully: %@", [group stringValue]);
} onError:^(CometChatException * error) {
    NSLog(@"Group joining failed with exception: %@", [error errorDescription]);
}];

Sample Payload - Join Public Group

Request Parameters:

Parameter	Type	Description
GUID	String	Unique group identifier. Example: `"cometchat-guid-1"`
groupType	GroupType	Type of group. Example: `.public`
password	String?	Password for the group. Example: `nil`

Success Response (Group Object):

Parameter	Type	Description
guid	String	Unique group identifier. Example: `"cometchat-guid-1"`
name	String?	Group display name. Example: `"Hiking Group"`
groupType	GroupType	Type of group. Example: `.public`
icon	String?	URL to the group’s icon image. Example: `"https://assets.cometchat.io/sampleapp/v2/groups/cometchat-guid-1.webp"`
groupDescription	String?	Description of the group. Example: `"Explore, connect, and chat with fellow outdoor enthusiasts"`
owner	String?	UID of the group owner. Example: `"cometchat-uid-5"`
membersCount	Int	Total number of members (incremented by 1). Example: `6`
hasJoined	Bool	Whether the logged-in user is a member. Example: `true`
joinedAt	Int	Unix timestamp when user joined. Example: `1772113500`
scope	MemberScope	User’s scope in the group. Example: `.participant`
createdAt	Int	Unix timestamp when group was created. Example: `1753861429`
tags	[String]	Array of tags. Example: `[]`
metadata	[String: Any]?	Custom metadata dictionary. Example: `[:]`

Success Response Properties After Join:

Property	Value After Join	Description
hasJoined	true	User is now a member
joinedAt	Unix timestamp	Time of joining
scope	.participant	Default scope for new members
membersCount	Incremented by 1	Updated member count

Error Response (CometChatException):

Parameter	Type	Description
errorCode	String	Unique error code. Example: `"ERR_ALREADY_JOINED"`
errorDescription	String	Human-readable error message. Example: `"User is already a member of this group"`

Sample Payload - Join Password Group

Request Parameters:

Parameter	Type	Description
GUID	String	Unique group identifier. Example: `"cometchat-guid-1"`
groupType	GroupType	Type of group. Example: `.password`
password	String	Password for the group (required). Example: `"test123"`

Success Response (Group Object):

Parameter	Type	Description
guid	String	Unique group identifier. Example: `"cometchat-guid-1"`
name	String?	Group display name. Example: `"Secret Group"`
groupType	GroupType	Type of group. Example: `.password`
icon	String?	URL to the group’s icon image. Example: `nil`
groupDescription	String?	Description of the group. Example: `nil`
owner	String?	UID of the group owner. Example: `"cometchat-uid-5"`
membersCount	Int	Total number of members. Example: `5`
hasJoined	Bool	Whether the logged-in user is a member. Example: `true`
joinedAt	Int	Unix timestamp when user joined. Example: `1772113600`
scope	MemberScope	User’s scope in the group. Example: `.participant`
createdAt	Int	Unix timestamp when group was created. Example: `1753861429`
tags	[String]	Array of tags. Example: `[]`
metadata	[String: Any]?	Custom metadata dictionary. Example: `[:]`

Error Response - Wrong Password:

Parameter	Type	Description
errorCode	String	Unique error code. Example: `"ERR_WRONG_GROUP_PASS"`
errorDescription	String	Human-readable error message. Example: `"Incorrect password for password-protected group"`

Sample Payload - Join Private Group (Error)

Request Parameters:

Parameter	Type	Description
GUID	String	Unique group identifier. Example: `"cometchat-guid-1"`
groupType	GroupType	Type of group. Example: `.private`
password	String?	Password for the group. Example: `nil`

Error Response:

Parameter	Type	Description
errorCode	String	Unique error code. Example: `"ERR_GROUP_JOIN_NOT_ALLOWED"`
errorDescription	String	Human-readable error message. Example: `"The private groups cannot be joined. Users need to be added to such groups."`

Private groups cannot be joined directly. Users must be added by an admin or owner.

Once you have joined a group successfully, you can send and receive messages in that group.

CometChat keeps a track of the groups joined and you do not need to join the group every time you want to communicate in the group. You can identify if a group is joined using the hasJoined parameter in the Group object.

Real-time Group Member Joined Events

In other words, as a recipient, how do I know when someone joins a group? To receive Real-Time Events for the same, you need to implement the onGroupMemberJoined() method of the CometChatGroupDelegate.

Swift
Objective C

class ViewController: UIViewController, CometChatGroupDelegate {
    
    override func viewDidLoad() {
        super.viewDidLoad()
        CometChat.groupdelegate = self
    }
    
    func onGroupMemberJoined(action: ActionMessage, joinedUser: User, joinedGroup: Group) {
        print("\(joinedUser.name ?? "") joined \(joinedGroup.name ?? "")")
    }
    
    func onMemberAddedToGroup(action: ActionMessage, addedBy: User, addedUser: User, addedTo: Group) {
        print("\(addedUser.name ?? "") was added to \(addedTo.name ?? "")")
    }
}

@interface ViewController ()<CometChatGroupDelegate>
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    [CometChat setGroupdelegate:self];
}

- (void)onMemberAddedToGroup:(Action *)action addedBy:(User * _Nonnull)addedBy addedUser:(User * _Nonnull)addedUser addedTo:(Group * _Nonnull)addedTo {
    // When any member is added in the group this function will be called
}

@end

Sample Payload - onGroupMemberJoined Event

Event Trigger: Received via CometChatGroupDelegate.onGroupMemberJoined(action:joinedUser:joinedGroup:)ActionMessage Object:

Parameter	Type	Description
action	String	Action type. Example: `"joined"`
actionBy	User	User who performed the action. Example: `{"uid": "user123", "name": "John"}`
actionFor	Group	Group where action occurred. Example: `{"guid": "group123", "name": "My Group"}`

joinedUser (User Object):

Parameter	Type	Description
uid	String?	Unique identifier of the user who joined. Example: `"user123"`
name	String?	Display name of the user. Example: `"John Doe"`
avatar	String?	URL to the user’s avatar image. Example: `"https://example.com/avatar.png"`
status	UserStatus	Current online status. Example: `.online`

joinedGroup (Group Object):

Parameter	Type	Description
guid	String	Unique group identifier. Example: `"group123"`
name	String?	Group display name. Example: `"My Group"`
membersCount	Int	Updated member count. Example: `16`

Missed Group Member Joined Events

In other words, as a member of a group, how do I know if someone joins the group when my app is not running? When you retrieve the list of previous messages if a member has joined any group that the logged-in user is a member of, the list of messages will contain an Action message. An Action message is a sub-class of BaseMessage class. For the group member joined event, in the Action object received, the following fields can help you get the relevant information:

Field	Value	Description
action	`"joined"`	Action type
actionBy	User object	User who joined the group
actionFor	Group object	Group the user joined

GroupType Enum

Value	Description
.public	Anyone can join without approval
.private	Requires invitation or approval to join
.password	Requires password to join

MemberScope Enum

Value	Description
.admin	Full control over group
.moderator	Can manage members and messages
.participant	Regular member with basic permissions

Common Error Codes

Error Code	Description	Resolution
ERR_NOT_LOGGED_IN	User is not logged in	Login first using `CometChat.login()`
ERR_GUID_NOT_FOUND	Group does not exist	Verify the GUID is correct
ERR_ALREADY_JOINED	Already a member of this group	No action needed
ERR_WRONG_GROUP_PASS	Incorrect password	Provide correct password
ERR_GROUP_JOIN_NOT_ALLOWED	Cannot join private group	Request admin to add you
ERR_USER_BANNED	User is banned from group	Contact group admin

​Join a Group

​Join Group Parameters

​Group Type Behavior

​Real-time Group Member Joined Events

​Missed Group Member Joined Events

​GroupType Enum

​MemberScope Enum

​Common Error Codes

Join a Group

Join Group Parameters

Group Type Behavior

Real-time Group Member Joined Events

Missed Group Member Joined Events

GroupType Enum

MemberScope Enum

Common Error Codes