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Questions tagged [non-nullable]

232 questions
229
votes
11 answers

Best explanation for languages without null

Every so often when programmers are complaining about null errors/exceptions someone asks what we do without null. I have some basic idea of the coolness of option types, but I don't have the knowledge or languages skill to best express it. What is…
Roman A. Taycher
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4 answers

In Kotlin, what is the idiomatic way to deal with nullable values, referencing or converting them

If I have a nullable type Xyz?, I want to reference it or convert it to a non-nullable type Xyz. What is the idiomatic way of doing so in Kotlin? For example, this code is in error: val something: Xyz? = createPossiblyNullXyz() something.foo() //…
Jayson Minard
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59
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1 answer

Why @Nonnull annotation checked at runtime?

I have a function with following signature public static String myFunction(@Nonnull String param) When I call it with param as null, I get the following exception: Caused by: java.lang.IllegalArgumentException: Argument for @Nonnull parameter…
Dmitry
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51
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3 answers

Create Non-Nullable Types in C#

How to create non-nullable value types like int, bool, etc. in C#?
Navid Rahmani
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42
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2 answers

Best practice for using Nullable Reference Types for DTOs

I have a DTO which is populated by reading from a DynamoDB table. Say it looks like this currently: public class Item { public string Id { get; set; } // PK so technically cannot be null public string Name { get; set; } // validation to…
BritishDeveloper
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6 answers

Why is null not allowed for DateTime in C#?

Why it is not allowed to assign null to a DateTime in C#? How has this been implemented? And can this feature be used to make your own classes non-nullable? Example: string stringTest = null; // Okay DateTime dateTimeTest = null; // Compile error I…
Jan Aagaard
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1 answer

How do I specify "any non-nullable type" as a generic type parameter constraint?

The post is specific to C# 8. Let's assume I want to have this method: public static TValue Get( this Dictionary src, TKey key, TValue @default ) => src.TryGetValue(key, out var value) ? value : @default; If my…
Alex Yakunin
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28
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4 answers

Make Kotlin warn on assignment of flexible/platform type to non-null type?

When calling a non-nullability-annotated Java function from Kotlin, we get flexible-typed return values, denoted by exclamation marks, e.g. String!. Kotlin silently allows assigning these flexible values to a normal non-null type, e.g. String, which…
Snild Dolkow
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28
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3 answers

Right way to use the @NonNull annotation in Android Studio

I'd like to use the @NonNull annotation in Android, but I can't figure out just the right way to do it. I propose you this example: public void doStuff(@NonNull String s){ //do work with s... } So when i call doStuff(null) the IDE will…
MMauro
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28
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8 answers

C# creating a non-nullable string. Is it possible? Somehow?

So you can't inherit string. You can't make a non-nullable string. But I want to do this. I want a class, let's call it nString that returns a default value when it would otherwise be null. I have JSON objects that might have who knows how many null…
Jared Price
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26
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7 answers

Making a Non-nullable value type nullable

I have a simple struct that has limited use. The struct is created in a method that calls the data from the database. If there is no data returned from the database I want to be able to return a null, but Visual Studio complains, Cannot convert null…
Malfist
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23
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11 answers

What would we do without NULL?

I once read that having nullable types is an absolute evil. I believe it was in an article written by the very person who created them(in Ada?) I believe this is the article Anyway, so what if by default a language like C# used non-nullable types?…
Earlz
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23
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2 answers

How can I get close to non-nullable reference types in C# today?

I've read many of the non-nullable questions and answers. It looks like the best way to get close to non-nullable types in C# (4.0) is Jon Skeet's NonNullable<> hack. However, it seems that C++/CLI has solved much of the problem by supporting…
Ðаn
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3 answers

Make a column nullable in DB2 when Data Capture is enabled

I'm using db2 version 9.7* and it seems impossible to make a NOT NULL column nullable in any straightforward way. Unfortunately the solution of using a more developer friendly database is not available. Basically, in MySQL speak, I want to do…
lukewm
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2 answers

Is constructor the only way to initialize non-nullable properties in a class in C#?

I have switched to enable nullable in my project that uses C#8. Now I have the following class: public class Request { public string Type { get; set; } public string Username { get; set; } public string Key { get; set; } } Compiler of…
Ilya Chernomordik
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