C#•14mo ago

I'm having trouble with an IndexOf returning the position in a array

I looked online and wasn't able to find a solution so any help would be appreciated.

25 Replies

Besties.cs

so which line is the culprit, what did you expect and what was actually happening?

line 36. I was expecting it to find the position of the name entered, return the value and then print the friend's details.

HimmDawg•14mo ago

You have a Friend[] but you are actually searching with a string

int pos = Array.LastIndexOf(friends, Nombre);

int pos = Array.LastIndexOf(friends, Nombre);

This method would only work if Nombre was a Friend

joejoejoe•14mo ago

That's right. For instance, on the initial prompt to enter friend details into the array, I include "John". Later, I would be prompted again to find the birthday of the friend I want. If I type in "John" it should return the array position of that friend. The program is not doing that.

HimmDawg•14mo ago

Yeah, I know Does it have to be LastIndexOf specifically?

joejoejoe•14mo ago

No. Anything that works would be fine with me lol

HimmDawg•14mo ago

Multiple ways to do it: - loop through the friends and just do some if-magic - use System.Linq and directly obtain the Friend with Friend? f = friends.LastOrDefault(f => f.Name == Nombre);. Instead of checking for the index, you can check f is null

joejoejoe•14mo ago

We haven't been taught how to use linq yet so it'll have to be a loop.

HimmDawg•14mo ago

Aight. Encapsulate it into a function then 😉

joejoejoe•14mo ago

Sorry I don't follow.

HimmDawg•14mo ago

You have a functionGetFriendData() This function encapsulates logic to obtain data and create a Friend object Makes it reusable and more readable Now do the same with "loop through my friend array and check if the name of the current friend is the name the user provided" Or well... you dont have to do it, but it looks nicer + has the aforementioned benefits

joejoejoe•14mo ago

Creating a function to loop through the array returned the same result. I must be missing something.

HimmDawg•14mo ago

How did you loop through your array? Also, can you provide the name you are providing for the data and for the search?

joejoejoe•14mo ago

Actually, I have another question, would a Array.IndexOf() even work in this context?

HimmDawg•14mo ago

https://learn.microsoft.com/de-de/dotnet/api/system.array.indexof?view=net-7.0#system-array-indexof(system-array-system-object)

Array.IndexOf Methode (System)

Sucht das angegebene Objekt und gibt den Index seines ersten Auftretens in einem eindimensionalen Array oder in einem Elementbereich im Array zurück.

HimmDawg•14mo ago

As you can see

public static int IndexOf (Array array, object? value);

public static int IndexOf (Array array, object? value);

expects an object? as second parameter. The function would try to match any element of the array with that object But since you are providing a string, it'd try to compare Friend objects with a string

joejoejoe•14mo ago

If the Friend objects aren't string values, then what are they?

HimmDawg•14mo ago

They are Friend objects Friends are Friends and strings are strings But your Friend object contains a property that is a string Name

joejoejoe•14mo ago

I understand what you mean but if the user input is a string data type how do I covert it to a Friend data type?

HimmDawg•14mo ago

You don't. Your idea is the other way around. You don't convert a string to a Friend. All you need to do is to take a Friends Name property and compare this to the user input. Both are strings, so they can be compared

Pobiega•14mo ago

List<Friend> friends = new();

// pretend we add some friends here...

string lookingForName = "Steve";

foreach (var friend in friends)
{
    // how do we check if `friend` has the name "Steve" here?
}

List<Friend> friends = new();

// pretend we add some friends here...

string lookingForName = "Steve";

foreach (var friend in friends)
{
    // how do we check if `friend` has the name "Steve" here?
}

Haze.•14mo ago

are my eyes deceiving me, or are your sub routines all in Main?

Pobiega•14mo ago

they are indeed local functions declared inside Main.

Haze.•14mo ago

thats painful

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I'm having trouble with an IndexOf returning the position in a array