I have a QVariantMap whose key is a string and value is an array(of ints or strings)
How do I get the individual elements of the array?
map["key"] has a method toList(). Can I apply that to arrays?
Yes,
QString first_string_of_key = QVariantMap["key"].toList()[0];
but this is only for reading. Any attempt to write will not work because QVariant will return a copy of the list. Read this post: Assigning to nested QVariantMap
Maybe you can try this if we say that we have an iterator it moving around the keys:
we could say
if(it.value("key").type()==QMetaType::ByteArray)
std::vector<std::string> vs_array_valus(QVariantMap["key"].value().toArray());
Or direct use as below:
if(QVariantMap["key"].value().type()==QMetaType::ByteArray)
std::vector<std::string> vs_array_valus(QVariantMap["key"].value().toArray());
Hope this Will help.
Related
In Qmetry,Trying to save array of arraylist string and access same in another test case.
Array of array list :
ArrayList<ArrayList<String>> my_list
store(my_list, "array_list_1");
//Accessing saved list
Object list_details = getBundle().getObject(array_list_1);
System.out.println("++++ saved list details++++" + list_details);
I am able to print list_details content. Till this there is no issue. But when I try to get the first index within the arraylist, not able to use .get(0) method. Below is the code.
ArrayList<String> list_details1 = list_details.get(0);
When tried typecasting , got an error 'java.lang.String cannot be cast to java.util.ArrayList'
typecast:
ArrayList<ArrayList<String>>list_details1 = (ArrayList<ArrayList<String>>)list_details;
Need to know is it the right way to store and access arraylist ? Please suggest.
if you want store in file, you can use .csv or .xls to save ArrayList<ArrayList> my_list, if ArrayList<ArrayList> my_list you query from database, you can set as static variable, then you can use in different method
dartques = {'Color':[], 'Fruits':[], 'Hobbies':[]};
How to access the values using index in map?
I need to access only key or value using index.
Just like we do in list
=>list[1]
you can get it like this
var element = dartques.values.elementAt(0);
also for Dart 2.7+ you can write extension function
extension GetByKeyIndex on Map {
elementAt(int index) => this.values.elementAt(index);
}
var element = dartques.elementAt(1);
For accessing the values by index, there are two approaches:
Get Key by index and value using the key:
final key = dartques.keys.elementAt(index);
final value = dartques[key];
Get value by index:
final value = dartques.values.elementAt(index);
You may choose the approach based on how and what data are stored on the map.
For example if your map consists of data in which there are duplicate values, I would recommend using the first approach as it allows you to get key at the index first and then the value so you can know if the value is the wanted one or not.
But if you do not care about duplication and only want to find a value based on Index then you should use the second approach, as it gives you the value directly.
Note: As per this Answer By Genchi Genbutsu, you can also use Extension methods for your convenience.
Important:
Since the default implementation for Map in dart is LinkedHashmap you are in great luck. Otherwise Generic Map is known for not maintaining order in many programming languages.
If this was asked for any other language for which the default was HashMap, it might have been impossible to answer.
You can convert it to two lists using keys and values methods:
var ques = {'Color':['a'], 'Fruits':['b'], 'Hobbies':['c']};
List keys = ques.keys.toList();
List values = ques.values.toList();
print (keys);
print (values);
The output:
[Color, Fruits, Hobbies]
[[a], [b], [c]]
So you can access it normally by using keys[0], for example.
I have two tables in my rails app: properties and requests. Both tables have field called address. But in property address is always single value like Hollywood for example and in request table there could be complicated string like ["Hollywood", "Beverley Hills"]. My task is to get all properties which match by address. It means that if we have in request ["Hollywood", "Beverley Hills"] i need all properties that have address as Hollywood and all Beverley Hills. I tried something like this:
#properties = Property.where("address = ? ", #request.address)
and:
#properties = Property.where("address IN (?) ", #request.address)
but both variants don't work and i think because #request.address is actually string, not array.
So i would like if somebody would suggest me some good solution.
Your first try is wrong, as address in Property is a single value.
Your second try is correct but not the best.
You can use Property.where(address: #request.address). But you have to be sure that #request.address is an Array of String.
You shouldn't save an Array as a String like that: "[\"Hollywood\", \"Beverley Hills\"]. It is too hard to parse in the application. If you want to save this way, you will be better using serialize :address, Array in the model, because then it will return an Array when you try to access the attribute.
Anyway, check if #request.address in an Array of String, if not, parse it to be an Array of String.
You can just wrap it in an array
#properties = Property.where(address: [#request.address])
Pretty simple and straightforward question.
I have a jsonArray, and i want to delete an item by index. How do I do that?
I tried using the solution from here:
https://github.com/SwiftyJSON/SwiftyJSON/issues/439
Like this:
jsonArray[row]["Likers"].array!.dictionaryObject?.removeValueForKey(index)
But I got this error:
value of type json has no member dictionaryObject
Finally I found the answer to remove an element in JSON (array type) created by SwiftyJSON:
dataObj.arrayObject?.removeAtIndex(m)
By the way, to remove an element when JSON returned by SwiftyJSON in a dictionary type:
jsonObj.dictionaryObject?.removeValueForKey(keyValue)
I'm getting this answer form THIS
you just use
yourJsonArry.removeAtIndex(2)
Hear you just pass the index that you want to remove items
Right now I am using ArrayCollection. But I want to change that to Set as I want make sure do duplicate values come.
var addressList:ArrayCollection = new ArrayCollection();
One way is I can use Dictionary and store addresses as a key. And I can just use keys to iterate.
But I am looking for Java HashSet like implementation.
You want to download Polygonal Data Structures. The swc contains a HashSet. If you want Java-style template syntax for Flash, you should also check out Haxe.
The AS3 equivalent to HashMap or HashSet is the Dictionary class, and to a lesser extent, the Object class. Object keys are stored as strings, while with Dictionary the keys are objects. You can't have duplicate entries with either. Are you looking for a specific implementation other than that?