Pass Array of objects from LWC to Apex controller

Question

I am trying to pass an array of objects from LWC to Apex but getting the error "Attempt to de-reference a null onbject". I googled and tried every possible way, but nothing seems to be working. What am I doing wrong. Below is my basic code snippet.

Map in LWC --

lwcmap = [{"key":"1","value":"test1"},{"key":"2","value":"test2"},{"key":"3","value":"test3"}]

method in LWC calling apex --

updateLVFilterData({MapofLWC : this.lwcmap}).then(data => {
 
 
}

Apex controller --

@AuraEnabled
    public static void mapofLWC( Map<Integer, String> MapofLWC){
        

        system.debug('MapofLWC - '+MapofLWC);
        
        }
        

Answer 1

1. For Map<Integer,String> data type you are passing an Array of Objects of type containing String:String {"key":"1","value":"test1"} which is incorrect
2. You need to set List<Map<string,String>> in your Aura Handler Apex Class, change it to this mapofLWC(List<Map<String, String>> MapofLWC) in your apex class
3. The other workaround is that serialize your lwcMap object which would make it a string
4. And in your aurHandler just make the input variable as String input
5. And deserialize the input in your auraHandler Apex Class

Answer 2

public static void mapofLWC( Map<Integer, String> MapofLWC){

Should be:

public static void mapofLWC(List<Map<String, String>> MapofLWC){

Based on the demo JSON.

If you wanted to use the original Apex parameter data type, your JSON should look like:

lwcmap = {1: "test1", 2: "test2", 3: "test3"}

Answer 3

What you have in LWC is not a map, is a List (see it's an array, '[]'). So that what Apex should receive is a List<>.

Now the question is, list of what?

What you have in there is a Wrapper Object (inner class) that you can build, with the attribute 'Integer key', and the attribute 'String value'. If you want a map, it will be only valid a map of <String,String> in this case because a JSON is a Map with a String key, so you could pass something like this [{"1":"test1"},{"2":"test2"}] and in this case it could be a List<Map<String,String>>.

Hope it helps.