Leppie's interesting suggestion to use 'Anonymous Classes' ... Re: Tuples in Functions - C# Discussion Boards

WebMaster18-Aug-12 9:53

18-Aug-12 9:53

Yeah, you are right; But my point was about "how to extend our return values count".
If you disagree with params, just overload the method.

Meysam

Re: Tuples in Functions

Keith Barrow18-Aug-12 9:38

Keith Barrow

18-Aug-12 9:38

OK, I realise I suggested the Tuple thing in the thread below. What you have will work (when fixed) and is arguably correct. However if the return value "means" something as a pair it would be better in a language like C# creating a class or struct to contain them. One rule of thumb is if you can give your return "thing" a sensible name. Let's say for the sake of argument the return values represent a x/y co-ordinate pair. If this were the case then you'd be better of creating a class or struct. If the values are really two results from a calculation (as you have in your example) a tuple is good. The point of the class is that it gives semantic meaning to your program, which developers that follow you can understand.

[Edit]
This came to me after reading Bill's reply below. One thing that you also need to consider with the tuple is that it is reliant on the code consuming the class knowing what order the values were put in (and your code putting them in the right order), if you were returning say a string and a double there would be less problem. That said creating a container class or struct the values would be explicitly named, reducing the potential for error.

Hopefully this isn't too confusing, getting to grips with programming is quite a task. This is a good read[^] if you are just starting out, it isn't as negative as the first few paragraphs suggest.

Sort of a cross between Lawrence of Arabia and Dilbert.[^]
-Or-
A Dead ringer for Kate Winslett[^]

modified 18-Aug-12 16:35pm.

Re: Tuples in Functions

BillWoodruff18-Aug-12 9:43

BillWoodruff

18-Aug-12 9:43

Between the responses to your first post, the responses to this post, and the (strangely out of place) discussion on the Lounge[^], you have a of ideas, and alternate strategies for using Tuples.

I want to respond directly to your question about using Tuples. In my opinion, they can best be described as a "bag of pairs" where, for every pair in the bag: the first element, of the pair, is a Type; and, the second element is a value of that Type.

And, do keep in mind that Tuples were introduced in .NET 4.0.

So, they are most appropriate, imho, if you need to return a bunch of different types: if every Type in your Tuple elements is the same: then use one of the other strategies, or a generic List<Type>, or another method.

Let me try and make this concrete for you: you can download this project (with source) compiled against .NET 4.0 here:[^].

1. create a simple 'WinForms application: drop a 'CheckBox, a 'DateTimePicker, a 'TextBox, and a 'NumericUpDown[1] on the main Form.

2. put two 'Buttons on the Form: title the first 'Button "Save Tuple," and the second "Restore Tuple."

Now let's look at what happens using a real Tuple in action: (attention: code-style obsessive-compulsives: I am using extra indentation, and line-breaks, here for clarity for the OP, it would not be my standard style):

1. first you declare a Form-scoped variable of Type Tuple for re-use:

private Tuple<CheckState, DateTime, string, decimal> _fourTuple;

1. You run the application, change the values of any of the four controls any way you like, and click the "Save Tuple" button: this code executes:

private void SaveTupleButtonClick(object sender, EventArgs e)
{
    _fourTuple = Tuple.Create
    (
        checkBox1.CheckState,
        dateTimePicker1.Value,
        textBox1.Text, 
        numericUpDown1.Value
    );
}

Here I am using the static Tuple.Create method, which was introduced in .NET FrameWork 4.0, to save some typing; it's exactly the same as if I wrote the fuller version:

private void SaveTupleButton_Click(object sender, EventArgs e)
{
    _fourTuple = new Tuple<CheckState, DateTime, string, decimal>
    (
        checkBox1.CheckState,
        dateTimePicker1.Value,
        textBox1.Text, 
        numericUpDown1.Value
    );
}

And now: what ? Well, you've saved the current values of these diverse types of Controls in your tuple. So, go ahead and change the values of all the Controls, and hit the "Restore Tuple" 'Button:

private void RestoreTupleClick(object sender, EventArgs e)
{
    checkBox1.CheckState = _fourTuple.Item1;
    dateTimePicker1.Value = _fourTuple.Item2;
    textBox1.Text = _fourTuple.Item3;
    numericUpDown1.Value = _fourTuple.Item4;
}

I hope you will see the controls' values reset to the exact value they were: when you pressed the "Save Tuple" 'Button.

Hope this example gives you some ideas.

best, Bill

[1] Keep in mind that 'NumericUpDownControls have 'Minimum and 'Maximum value settings, as well as a 'DecimalPlaces property: if you type in a value out of range: it will revert to the nearest min or max value: this can have a confusing run-time effect for the end user.

"One of the few good things about modern times: If you die horribly on television, you will not have died in vain. You will have entertained us." Kurt Vonnegut

My Vote of 5

Keith Barrow18-Aug-12 10:32

Keith Barrow

18-Aug-12 10:32

Vote of 5: Coherent, well though out and correct. I'd have been tempted to suggest we also have n-Tuple generics(ish), which if I had my way I'd have called then nuples.

Sort of a cross between Lawrence of Arabia and Dilbert.[^]
-Or-
A Dead ringer for Kate Winslett[^]

Re: Tuples in Functions

leppie18-Aug-12 21:37

leppie

18-Aug-12 21:37

While anonymous classes will not here, in this situation based on the amount of usage and 'decoration' required, a concrete class IMO would be a better option.

Remember you only have to write it once.

struct State
{
  public CheckState Value;
  public DateTime When;
  public string By;
  public decimal Amount;
}

A struct already implements hashcode and equality too.

Now imagine you need an extra field. In the case of a class/struct, no problem, but your Tuple will require changes across the board, even if you just add it to the end.

IronScheme
<small>((λ (x) `(,x ',x)) '(λ (x) `(,x ',x)))</small>

Re: Tuples in Functions

BillWoodruff19-Aug-12 14:15

BillWoodruff

19-Aug-12 14:15

Thanks, Leppie, for "weighing in here:" your comment on anonymous classes has lead me to some interesting technical geography.

Of course, I am still eager to here how you use anonymous classes

I've been reading, on various web-sources, mainly StackOverFlow, discussions of anonymous classes: the problem with SO is that while the OP may mention the words "anonymous classes," the discussion soon turns, it seems, to anonymous types, and use of 'dynamic, and 'var.

This SO thread was interesting for the sheer volume of responses and debates:"A generic list of anonymous class"[^].

Probably the two most interesting (and exotic) discussions I found were by Jon Skeet: "Horrible grotty hack: returning an anonymous type instance"[^], and on a site called DevCurry: "Look Ma! No Classes – Creating Generic List(T) collection of Anonymous Types and calling Extension Methods"[^].

In the comments section of the Skeet article is this wonderful exchange between Jon and one "Erik:"

# re: Horrible grotty hack: returning an anonymous type instance
"This is one of those examples where relying on internal implementations can bite you, I imagine - since anonymous types are by design not supposed to leave private scope, the compiler team is free to do whatever they want with the actual implementation.
Thanks for the brain-twitch, though, Jon. =)
Friday, January 09, 2009 12:21 PM by Erik"

# re: Horrible grotty hack: returning an anonymous type instance
"@Erik: No, it's not implementation-dependent. The compiler-generated name is, but the language spec guarantees that two anonymous object creation expressions using the same property names and compile-time types within the same assembly will create instances of the same type. See section 7.5.10.6 of the C# 3.0 spec.
Friday, January 09, 2009 1:48 PM by skeet"

best, Bill

"One of the few good things about modern times: If you die horribly on television, you will not have died in vain. You will have entertained us." Kurt Vonnegut

Re: Tuples in Functions

leppie19-Aug-12 19:41

leppie

19-Aug-12 19:41

Quote:
I am still eager to here how you use anonymous classes

In the aforementioned case, it would be impossible Smile | :)

The rest of the possible cases is indeed described by Jon Skeet, and while he calls them a 'hack', any of those ways should be preferred over tuples (IMO).

IronScheme
<small>((λ (x) `(,x ',x)) '(λ (x) `(,x ',x)))</small>

Leppie's interesting suggestion to use 'Anonymous Classes' ... Re: Tuples in Functions

BillWoodruff18-Aug-12 15:49

BillWoodruff

18-Aug-12 15:49

Leppie wrote[^] re: the discussion of the use of Tuples (on the Lounge):

"Anonymous classes handle most of these cases and cleaner in my opinion.
Who knows what Item0 and Item1 and Item2 is?"

.Of course Leppie is absolutely right: Tuple elements cannot be accessed by index; they cannot be foreach iterated, and, the following "legal" way to find out, at run-time, what Type an Item1 ... Item#n is, for example: "_fourTuple.Item1.GetType();" is something that would make me gag if I saw it in "real code."

The main reason I am writing this is to ask Leppie to please reply with an example of the use of anonymous classes, which interests me very much, and I think will add value to this discussion.

thanks, Bill

"One of the few good things about modern times: If you die horribly on television, you will not have died in vain. You will have entertained us." Kurt Vonnegut

Re: Leppie's interesting suggestion to use 'Anonymous Classes' ... Re: Tuples in Functions

BobJanova20-Aug-12 1:00

BobJanova

20-Aug-12 1:00

I agree in general but you know, statically, what the type of the second item of a Tuple is. If the Tuple is Tuple<T, U> then the type of the second item is U.

Trying to Obtain Two (2) Values from Function

computerpublic16-Aug-12 21:53

computerpublic

16-Aug-12 21:53

Hello,
In the following function, I am trying to return two (2) values instead of one. Can someone please say how this can be done? I was thinking possibly returning an array from the function, but I do not know if this is possible. Does anyone have an idea of how multiple values can be obtain from the same function?
Thanks.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Testing_Functions
{
    class Program
    {
        public static Double Test(Double Val1, Double Val2, Double Val3)
        {
            Double Test_Val = Val1 + Val2 + Val3;
            Double Second_Test = Test_Val % 2;
            return Test_Val;
            //return Second_Test;//I need to return this value also(two values, NOT ONE.)
        }
        static void Main(string[] args)
        {
            Double A = 1, B = 2, C = 3;
            Double Result = Test(A,B,C);
            //Double Result_2 = Test(A, B, C);
        }
    }
}

Re: Trying to Obtain Two (2) Values from Function

DaveyM6916-Aug-12 22:36

DaveyM69

16-Aug-12 22:36

There are a few ways of obtaining multiple values.

1. Create an struct/class that holds more than one value
2. Use an array or list (the same as 1 really)
3. Use an out (or ref if needed) parameter.

1:

public class Pair<T>
{
    private T first;
    private T second;

    public Pair(T first, T second)
    {
        this.first = first;
        this.second = second;
    }

    public T First { get { return first; } }
    public T Second { get { return second; } }
}

public static Double Test(Double Val1, Double Val2, Double Val3)
{
    Double Test_Val = Val1 + Val2 + Val3;
    Double Second_Test = Test_Val % 2;
    return new Pair<Double>(Test_Val, Second_Test);
}

2 should be straight forward.

3:

public static Double Test(Double Val1, Double Val2, Double Val3, out Double secondResult)
{
    Double Test_Val = Val1 + Val2 + Val3;
    secondResult = Test_Val % 2;
    return Test_Val;
}

Dave

Binging is like googling, it just feels dirtier.
Please take your VB.NET out of our nice case sensitive forum.
Astonish us. Be exceptional. (Pete O'Hanlon)

BTW, in software, hope and pray is not a viable strategy. (Luc Pattyn)

Re: Trying to Obtain Two (2) Values from Function

BobJanova16-Aug-12 22:54

BobJanova

16-Aug-12 22:54

out and ref parameters are usually considered to be dirty, so stay away from that if you can.

Depending on what the function does, you may want to create a wrapper class or struct for the result. That means that you get semantically useful names, instead of First and Second from the Pair class.

Re: Trying to Obtain Two (2) Values from Function

Keith Barrow17-Aug-12 2:12

Keith Barrow

17-Aug-12 2:12

Also, he could return a Tuple<type,type> but by far the best is solution 1.

Sort of a cross between Lawrence of Arabia and Dilbert.[^]
-Or-
A Dead ringer for Kate Winslett[^]

Re: Trying to Obtain Two (2) Values from Function

Sangramsingh Pawar17-Aug-12 0:43

Sangramsingh Pawar

17-Aug-12 0:43

Use  ref and out keyword to return multiple values from function
return statement returns only single value.

Re: Trying to Obtain Two (2) Values from Function

V.17-Aug-12 3:16

17-Aug-12 3:16

the quick and dirty way:

public static Double[] Test(Double Val1, Double Val2, Double Val3)
        {

            Double Test_Val = Val1 + Val2 + Val3;
            Double Second_Test = Test_Val % 2;
            double [] arr = { Test_Val, Second_Test };
            return arr;
            //return Second_Test;//I need to return this value also(two values, NOT ONE.)
        }

Just to show you, you can return virtually anything, including Lists, Dictionaries, self made object (like the Pair example)

Re: Trying to Obtain Two (2) Values from Function

Kuthuparakkal17-Aug-12 16:05

Kuthuparakkal

17-Aug-12 16:05

A Class (object) is the best way. But if you do not have more than two values, you can always use a Dictionary<>, or KeyValuePair etc
System.Collections.Generic.Dictionary<tkey, tvalue=""> : http://msdn.microsoft.com/en-us/library/xfhwa508.aspx
KeyValuePair<tkey, tvalue=""> : http://msdn.microsoft.com/en-us/library/5tbh8a42.aspx

How to insert,update and edit data in datagridview window form

ope4sure116-Aug-12 19:54

ope4sure1

16-Aug-12 19:54

Please am working on an application that use datagrid view but am looking for tutorial or code that i can use to insert,update record that i retrieved from the database.

Re: How to insert,update and edit data in datagridview window form

Calla16-Aug-12 20:53

Calla

16-Aug-12 20:53