How to create url with complex query - api

Question

I use dart and flutter for mobile app. I use my api to get data from server. But I found a problem, maybe its dart core problem.
I need to add complex queryParams to my URL like
Map<String, Map<String, List<String>>>{"a": {"b": ["c","d"]}, "e": {}}
I use Uri.parse(url).replace(queryParams: myQueryParams).toString()
But Uri.replace() accepts only Map<String, Iterable<String>> and throws an error
Unhandled Exception: type '_InternalLinkedHashMap<String, List<String>>' is not a subtype of type 'Iterable<dynamic>'
I found method which throws this error
static String _makeQuery(String query, int start, int end,
Map<String, dynamic /*String|Iterable<String>*/ > queryParameters) {
if (query != null) {
if (queryParameters != null) {
throw ArgumentError('Both query and queryParameters specified');
}
return _normalizeOrSubstring(query, start, end, _queryCharTable,
escapeDelimiters: true);
}
if (queryParameters == null) return null;
var result = StringBuffer();
var separator = "";
void writeParameter(String key, String value) {
result.write(separator);
separator = "&";
result.write(Uri.encodeQueryComponent(key));
if (value != null && value.isNotEmpty) {
result.write("=");
result.write(Uri.encodeQueryComponent(value));
}
}
queryParameters.forEach((key, value) {
if (value == null || value is String) {
writeParameter(key, value);
} else {
Iterable values = value;
for (String value in values) {
writeParameter(key, value);
}
}
});
return result.toString();
}
So my question is there is some method in dart to add my queryParams to url or I need to create it by my own?

Answer 1

I have modified original method and now its work.
class UrlCreator {
static String addQueryParams(String url, Map<String, dynamic> queryParams) {
var result = StringBuffer();
var separator = "";
void writeParameter(String key, String value) {
result.write(separator);
separator = "&";
result.write(Uri.encodeQueryComponent(key));
if (value != null && value.isNotEmpty) {
result.write("=");
result.write(Uri.encodeQueryComponent(value));
}
}
void buildQuery(Map queryParams, {parentKey}){
queryParams.forEach((key, value){
print("parentKey = $parentKey Key = $key value = $value");
if (value == null || value is String) {
var newKey = parentKey != null ? "$parentKey[$key]" : key;
writeParameter(newKey, value);
} else if (value is Map) {
buildQuery(value, parentKey: key);
} else {
Iterable values = value;
var newKey = parentKey != null ? "$parentKey[$key][]" : "$key[]";
for (String value in values) {
writeParameter(newKey, value);
}
}
});
}
buildQuery(queryParams);
return url + "?" + result.toString();
}
}