How does the Dart URI class QueryParameters handle Map values?

Question

According to the documentation, it needs to follows the Form Post rules at: https://www.w3.org/TR/REC-html40/interact/forms.html#h-17.13.4. When looking at that information it did not give me much to work with in terms of complex objects or maps.

Right now, If I have a list for example: Each item in the list needs to be stringified.

var params = {"list": [1,2,3]};
// needs to be stringed.
params["list"] = params["list"].map((item)=>item.toString()).toList();

Simple. Also all base items need to be a string as well

var params = {"number": 1, "boolean": true};
params = params.forEach((k,v)=> params[k].toString());

But how do we handle maps?

var params = {"map": {"a":1,"b":"foo","c":false,"d":[]}};
// ??

It seems that after testing in my app and in dart pad, you need to make sure everything is strings, so i am trying to come up with a way to effectively cover lists, maps, and maybe more complex objects for encoding.

var params = {};
params["list"] = [1,2,3];
params["number"] = 1;
params["boolean"] = true;
params["map"] = {"a":1,"b":"foo","c":false,"d":[]};
params.forEach((String key, dynamic value){
  if(value is List){
    params[key] = value.map((v)=>v.toString()).toList();
  }else if(value is Map){
    // ????
  }else{
    params[key] = value.toString();
  }
  //maybe have an additional one for custom classes, but if they are being passed around they should already have their own JSON Parsing implementations.
}

Ideally, the result of this would be passed into:

Uri myUri = new Uri(queryParameters: params);

and right now, while i solved the list issue, it doesn't like receiving maps. Part of me just wanted to stringify the map as a whole, but i wasn't not sure if there was a better way. I know that when someone accidentally stringified the array, it was not giving me: ?id=1&id=2 but instead ?id=%5B1%2C2%5D which was not correct.

Günter Zöchbauer · Accepted Answer · 2017-08-23 14:34:43Z

2

I don't think there is any special support for maps. Query parameters itself is a map from string to string or string to list-of-strings.

Everything else need to be brought into this format first before you can pass it as query parameter.

A simple approach would be to JSON encode the map and pass the resulting string as a single query parameter.

answered Aug 23, 2017 at 14:34

Günter Zöchbauer

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2 Comments

Fallenreaper Over a year ago

that's actually what i was thinking would be the end state, just encode the map and then send it on its way. I wasn't sure if there was a specific standard I should be adhering to regarding it though.. Also Great speaking with ya again Gunter. :) I dont want to tag it quite yet as the answer, as maybe there is different input into the matter.

Günter Zöchbauer Over a year ago

Sure, no worries. It's entirely up to you if or when to accept an answer.

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