add nested map value like Map<String,Map<String,String>>

Question

var stars = new Map<String,Map<String,String>>();
  Map<String,String> xx = {
    'test' : 'test'
  };
  stars.putIfAbsent('String', xx);

im getting this error the argument type Map<String,String> cant be assigned to the parameter type Map<String,String>Function(), i don't know what's this Function() at the end of the map, i know this maybe a stupid question but i really dont know where to read about it because i found nothing helpful at official dart docs . thanks in advance

As @Ovidiu as said, the parameter 'xx' should be a function and not a value. Check the docs here: api.dartlang.org/stable/2.4.1/dart-core/Map/putIfAbsent.html — Ike Mawira
– Ike Mawira, Commented Aug 10, 2019 at 22:51
thanks. i just needed this peace of documentation. actually i thought there is something with map structure not with putIfAbsent. thank you again — evals
– evals, Commented Aug 11, 2019 at 4:40
if you found the comment helpful, don't forget to upvote it. Thanks. — Ike Mawira
– Ike Mawira, Commented Aug 12, 2019 at 8:16
i wish you have put your comment in answer i will accept it since i was looking for documentation more than a peace of code — evals
– evals, Commented Aug 12, 2019 at 9:44

Ovidiu · Accepted Answer · 2019-08-10 20:11:13Z

2

putIfAbsent requires the 2nd parameter to be a function, not a value. Try this code:

stars.putIfAbsent('String', () => xx);

answered Aug 10, 2019 at 20:11

Ovidiu

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