dart language: Map<Object,String> how to add new pair?

Question

Given:

Map<WebSocket,String> mListUser;
mListUser= new  Map<WebSocket,String>();

From what i understood now to add a new element i should just do:

mListUser[socket]="string";

instead im getting:

type 'String' is not a subtype of type 'int' of 'index'.

What am i doing wrong?

Based on the error I'd say mListUser is a List, not a Map. Is this the original, real code that you copied? — MarioP
– MarioP, Commented Aug 12, 2013 at 7:09
i was using before a list and forgot to change the name, am defenetly using a map. As Gero as shown, i think im doing it right way, i guess there is something wrong in the object i use as a key, which by the way is the same Websocket i get from the onConnection on the Chathandler class (source here dartlang.org/docs/dart-up-and-running/contents/ch05.html) — user1964154
– user1964154, Commented Aug 12, 2013 at 9:55
Well, without any further info, I can just stubbornly reiterate: The error message says that somewhere, you are trying to assign a String to a variable or parameter named "index", which has to be an integer. If this is the real code, this error may not even relate to the map at all. — MarioP
– MarioP, Commented Aug 12, 2013 at 10:17

Dariusz Bacinski · Accepted Answer · 2019-07-09 07:53:26Z

36

Maybe it helps

final test = Map<String, int>();
test.putIfAbsent('58', () => 56);

if key doesn't exist, it will be putted into map.

edited Jul 9, 2019 at 7:53

Dariusz Bacinski

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answered Oct 7, 2018 at 16:58

Вячеслав Францишко

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1 Comment

Javier Chauvin Over a year ago

I am using a `Map<DateTime, Lis<Event>>' (Event is a random class). Every time I add a new pair, the key (DateTime) is correctly added, but the list is replaced in all keys. Any help? Any Ideas?

Gero · Accepted Answer · 2013-08-11 20:36:47Z

11

Maybe it helps.

Map<Object,String> map1= new Map<Object,String>();
Collections c = new Collections(); //some random class

map1[new Collections()]="arg1";
map1[c]="arg2";

map1.forEach((k,v)=>print("out: $k $v"));
print(map1[c]);

gets me this output:

out: Instance of 'Collections' arg2
out: Instance of 'Collections' arg1
arg2

answered Aug 11, 2013 at 20:36

Gero

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1 Comment

user1964154 Over a year ago

I found the problem or identify it. Since im using 'dart:io'; instead of import 'dart:html'; is seems that in the first, WebSocket is an abstract class and trying to use it as a key just doen't work, at least in that way. Note that in a project with 'dart:html'; everything works as expected as suggested above by Gero

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