CODEWITHSUNDEEP
c#arraylistdoubleint
Tim
Tim

Reputation: 429

JSON to C# : convert an arraylist of doubles to an array of ints?

I have an arraylist of doubles returned by a JSON library. After the JSON parser's decode method is run, we have this in the C# locals window:

Name     Value           Type
myObj    Count=4         object {System.Collections.ArrayList}
[0]      100.0           object {double}
[1]      244.0           object {double}
[2]      123.0           object {double}
[3]      999.0           object {double}

My goal is to produce an array of integers from this ArrayList. It would be simple to iterate and do this one value at a time, but I'd like to know how to do it using the built-in converter functionality. I have been reading theads on ConvertAll but I cannot get it to work.

I do not have control of the JSON library so I must begin with the ArrayList.

Thanks

Upvotes: 0

Views: 3011

Answers (5)

jason
jason

Reputation: 241641

You need to be careful with ArrayLists because of boxing. Thus:

// list is ArrayList      
int[] array = Array.ConvertAll(list.ToArray(), o => (int)(double)o);

Note the cast is framed as (int)(double). This first unboxes the boxed double and then casts to an int.

To do this in older versions of .NET

// list is ArrayList
int[] array = Array.ConvertAll(
    list.ToArray(),
    delegate(object o) { return (int)(double)o; }
);

An alternative is

// list is ArrayList
int[] array = Array.ConvertAll(
    (double[])list.ToArray(typeof(double)),
    o => (int)o
);

Here we do not need an unboxing operation because we have first converted the ArrayList to an array of unboxed doubles.

To do this in older versions of .NET

// list is ArrayList
int[] array = Array.ConvertAll(
    (double[])list.ToArray(typeof(double)),
    delegate(double o) { return (int)o; }
);

Upvotes: 1

Tristan Warner-Smith
Tristan Warner-Smith

Reputation: 9771

The linq options are cleaner, but if you don't have linq.

//Assuming someValues is your input array and you're sure you don't need to check the types
int[] outputValues = new int[someValues.Count];
for (int i = 0; i < someValues.Count; i++)
   outputValues[i] = (int)someValues[i];

Upvotes: 0

Anton
Anton

Reputation: 5623

If you want a sample of a working solution using ConvertAll, here's a quick snippet.

 public static void testCOnvertAll()
        {
            List<double> target = new List<double>();
            target.Add(2.3);
            target.Add(2.4);
            target.Add(3.2);

            List<int> result = target.ConvertAll<int>(new Converter<double, int>(DoubleToInt));

        }

        public static int DoubleToInt(double toConvert)
        {
            return Convert.ToInt32(toConvert);
        }

Upvotes: 0

Joel Etherton
Joel Etherton

Reputation: 37533

I would think something like this (with converter):

    private void Main()
    {
        List<Double> lstd = new List<Double>();

        lstd.Add(100.0);
        lstd.Add(244.0);
        lstd.Add(123.0);
        lstd.Add(999.0);

        List<int> lsti = lstd.ConvertAll(new Converter<double, int>(DoubleToInt));

    }


    public static int DoubleToInt(double dbl)
    {
        return (int)dbl;
    }

Upvotes: 1

Travis Gockel
Travis Gockel

Reputation: 27633

Linq:

var array = (from double d in list
             select (int)d).ToArray();

Upvotes: 2

Related Questions