Apex Wb Service POST method is not creating multiple child records on a parent record

Question

I have a Master-Detail object in my org, Ticket__c(parent/master) and Ticket_Task__c (detail/child). I created a Web Service whose PUT method is successfully creating new tasks for a given ticket number. The JSON response for the put is in this format:

[{
    "ticketName": "XYZ123",
    "taskNumber": "1265659",
    "assignedTo": "bLA BLA!"
},
{
    "ticketName": "ZZZ456",
    "taskNumber": "546",
    "assignedTo": "GSDSD"
},
 {
    "ticketName": "SDSF67",
    "taskNumber": "767",
    "assignedTo": "SDSFF"
  }
]

The problem comes when I want to create multiple tasks for the same ticketName. It only creates the last one. In other words if I want to create a task for the following JSON, then only the last one gets created:

[{
        "ticketName": "XYZ123",
        "taskNumber": "1265659",
        "assignedTo": "bLA BLA!"
    },
    {
        "ticketName": "XYZ123",
        "taskNumber": "546",
        "assignedTo": "GSDSD"
    }
    ]

Can someone explain to me why both tasks (2 details) for the Ticket (master) is not being created? My Apex code is below:

 @HttpPost
 global static List<Ticket_Task__c> createTicketTask(){
 RestRequest request = RestContext.request; 
 String jsonString = request.requestBody.toString();
 Map<String, Tasks> MapTicket = new Map<String, Tasks>();
 List<Tasks> tasklist = (List<Tasks>)JSON.deserialize(jsonString, List<Tasks>.class); 
 List<Ticket_Task__c> taskstoCreate = new List<Ticket_Task__c>();
 for(Tasks task : tasklist){
    MapTicket.put(task.ticketName, task);
 }

 List<Ticket__c> sticket = [SELECT Id, Name FROM Ticket__c WHERE Name IN: MapTicket.keySet()];

 for(Ticket__c st : sticket){
    Ticket_Task__c createTask = new Ticket_Task__c();
    createTask.Ticket__c = st.Id;
    createTask.Name = MapTicket.get(st.Name).taskNumber;
    createTask.Assigned_To__c = MapTicket.get(st.Name).assignedTo;
    taskstoCreate.add(createTask);
    }
        try{
            insert taskstoCreate;  
        }
        catch(DMLException e) {
            system.debug('***************************************** ' + e.getMessage()); 
            system.debug('***************************************** ' + e.getStackTraceString());
        } 
 
       return taskstoCreate;
    }

 global class Tasks {
        public String ticketName;
        public String taskNumber;
        public String assignedTo;
    }
   

Edited version:

@HttpPost
    global static List<Ticket_Task__c> createTicketTask(){
        RestRequest request = RestContext.request; 
        String jsonString = request.requestBody.toString();
        //Map<String, Tasks> MapTicket = new Map<String, Tasks>();
        Map<String, List<Tasks>> ticketNameWithTasks = new Map<String, List<Tasks>>();

        List<Tasks> tasklist = (List<Tasks>)JSON.deserialize(jsonString, List<Tasks>.class); 

        List<Ticket_Task__c> taskstoCreate = new List<Ticket_Task__c>();

        for(Tasks task : tasklist){
            if(ticketNameWithTasks.containsKey(task.ticketName)) {
                ticketNameWithTasks.get(task.ticketName).add(task); 
            } else {
                ticketNameWithTasks.put(task.ticketName, new List<Tasks>{task});
            }
            //MapTicket.put(task.ticketName, task);
        }

        List<Ticket__c> sticket = [SELECT Id, Name FROM Ticket__c WHERE Name IN: ticketNameWithTasks.keySet()];

        for(Ticket__c st : sticket){
            Ticket_Task__c createTask = new Ticket_Task__c();
            createTask.Ticket__c = st.Id;
            createTask.Name = ticketNameWithTasks.get(st.Name).taskNumber;
            createTask.Assigned_To__c = ticketNameWithTasks.get(st.Name).assignedTo;
            taskstoCreate.add(createTask);
        }
        try{
            insert taskstoCreate;  
        }
        catch(DMLException e) {
            system.debug('***************************************** ' + e.getMessage()); 
            system.debug('***************************************** ' + e.getStackTraceString());
        } 
 
        return taskstoCreate;
    }

Answer 1

My guess is because you are using the same ticket name for the key in the map.

"ticketName": "XYZ123"

A map needs to have a unique key for each key-value pair.

Trying using this logic and data struct:

@HttpPost
global static List<Ticket_Task__c> createTicketTask(){

   RestRequest request = RestContext.request; 
   String jsonString = request.requestBody.toString();
   Map<String, List<Tasks>> ticketNameWithTasks = new Map<String, List<Tasks>>(); 
   List<Tasks> tasklist = (List<Tasks>)JSON.deserialize(jsonString, List<Tasks>.class); 
   List<Ticket_Task__c> taskstoCreate = new List<Ticket_Task__c>();

   for(Tasks task : tasklist){
      if(ticketNameWithTasks.containsKey(task.ticketName)) {
         ticketNameWithTasks.get(task.ticketName).add(task); 
      } else {
         ticketNameWithTasks.put(task.ticketName, new List<Tasks>{task});
      }
   }
    
   for(Ticket__c st : [SELECT Id, Name 
                       FROM Ticket__c 
                       WHERE Name IN: ticketNameWithTasks.keySet()]){

      if(ticketNameWithTasks.containsKey(st.Name)) {
         for(Tasks t : ticketNameWithTasks.get(st.Name)) {

            Ticket_Task__c createTask = new Ticket_Task__c();
            createTask.Ticket__c = st.Id;
            createTask.Name = t.taskNumber;
            createTask.Assigned_To__c = t.assignedTo;

            taskstoCreate.add(createTask);
         }
      }
   }
        try{
            insert taskstoCreate;  
        }
        catch(DMLException e) {
            system.debug('***************************************** ' + e.getMessage()); 
            system.debug('***************************************** ' + e.getStackTraceString());
        } 
 
       return taskstoCreate;
    }

 global class Tasks {
        public String ticketName;
        public String taskNumber;
        public String assignedTo;
    }

}