dart null list
減少null判斷情況 https://stackoverflow.com/questions/51036758/flutter-the-method-map-was-called-on-null https://juejin.im/post/5c6d38b1f265da2dcc7feb69 https://cloud.tencent.com/developer/article/1370380 ?? => if null https://blog.csdn.net/ffa_ijj/article/details/85051156 return qres?.map((value) { LinkedHashMap result = json.decode(value["jsonitem"]); return result; })?.first ?? new LinkedHashMap(); 這個判斷方式有個問題，當查詢回來為[]，不是null情況下，在.first會出錯，因為 “No element"會出錯，但.toList()會正確，故改回 if (qres == null || qres.isEmpty) return new Member(); // 待確定是否出錯 var resmap = qres.first; return new Member.fromJson(json.decode(resmap["jsonitem"]));