Add/remove one element from a string set in DynamoDBItem - ios

Question

I am using DynamoDB for a social app based on events, like-unlike attending-not_attending.
I am interested in finding out how can add or remove an item from a StringSet attribute in DynamoDB Item.
Here is the objects structure
"userId": {
"S": "69"
},
"fName": {
"S": "mfName"
},
"lName": {
"S": "mlName"
},
"picture": {
"S": "https://s3-us-west-2.amazonaws.com/users/mfName_1000049788.jpg"
},
"events": {
"M": {
"1502199358": {
"M": {
"created": {
"S": "1502199358.443022"
},
"eventId": {
"S": "-1"
},
"galleryId": {
"S": "1502199358"
},
"image": {
"S": "https://s3.amazonaws.com/events/public/clyp_1502199358.jpg"
},
"likes": {
"SS": [
"12",
"321",
"69"
]
},
"modified": {
"S": "1"
},
"video": {
"S": "n_p"
},
"videothumb": {
"S": "n_p"
}
}
}
}
}
and I would like to add or remove one entry in "likes" StringSet
"likes": {
"SS": [
"12",
"321",
"69"
]
},
accordingly a user like-unlike the event.
how can I do this?

Answer 1

I did not get able to update/edit item on third or 4th child level.
Here you can use this method to add/delete item from a string set on second child level.
AWSDynamoDB *dynamoDB = [AWSDynamoDB defaultDynamoDB];
AWSDynamoDBAttributeValue * itemToUpdate = [AWSDynamoDBAttributeValue new];
itemToUpdate.S = self.userID;
AWSDynamoDBUpdateItemInput *updateItemInput = [AWSDynamoDBUpdateItemInput new];
updateItemInput.tableName = #"MyTable";
updateItemInput.key= #{
#"userId" : itemToUpdate
};
NSArray * likesArray = [NSArray arrayWithObjects:#"12", nil];
AWSDynamoDBAttributeValue * awsDynamoDBAttributeValue = [AWSDynamoDBAttributeValue new];
awsDynamoDBAttributeValue.SS = likesArray;
AWSDynamoDBAttributeValueUpdate * valueUpdate = [AWSDynamoDBAttributeValueUpdate new];
valueUpdate.value = awsDynamoDBAttributeValue;
valueUpdate.action = AWSDynamoDBAttributeActionDelete;
updateItemInput.attributeUpdates =#{
#"likes":valueUpdate
};
[[dynamoDB updateItem:updateItemInput]
continueWithBlock:^id(AWSTask *task) {
if (task.error) {
NSLog(#"The request failed. Error: [%#]", task.error);
}
if (task.result) {
//Do something with result.
}
return nil;
}];
-> for add an item
valueUpdate.action = AWSDynamoDBAttributeActionAdd;
-> for delete an item
valueUpdate.action = AWSDynamoDBAttributeActionDelete;
Hope it would help someone.