You ultimately have to decide what the null bool will represent. If null should be false, you can do this: bool newBool = x.HasValue ? x.Value : false; Or: bool newBool = x.HasValue && x.Value; Or: bool newBool = x ?? false;
The compiler is telling you that it doesn’t know how convert null into a DateTime. The solution is simple: DateTime? foo; foo = true ? (DateTime?)null : new DateTime(0); Note that Nullable<DateTime> can be written DateTime? which will save you a bunch of typing.
Short answer: I guess these annotations are only useful for your IDE to warn you of potentially null pointer errors. As said in the “Clean Code” book, you should check your public method’s parameters and also avoid checking invariants. Another good tip is never returning null values, but using Null Object Pattern instead.
From the clang documentation: The nullability (type) qualifiers express whether a value of a given pointer type can be null (the _Nullable qualifier), doesn’t have a defined meaning for null (the _Nonnull qualifier), or for which the purpose of null is unclear (the _Null_unspecified qualifier). Because nullability qualifiers are expressed within the type system, they … Read more
Use string instead of string? in all places in your code. The Nullable<T> type requires that T is a non-nullable value type, for example int or DateTime. Reference types like string can already be null. There would be no point in allowing things like Nullable<string> so it is disallowed. Also if you are using C# … Read more
According to MSDN – it’s down the page in the “Operators” section: When you perform comparisons with nullable types, if the value of one of the nullable types is null and the other is not, all comparisons evaluate to false except for != So both a > b and a < b evaluate to false … Read more
PHP 7.1 Now supports nullable return types. The first RFC I linked to is the one they went for: function nullOrString(int $foo) : ?string { return $foo%2 ? “odd” : null; } old answer: Since my comment was actually an answer to the question: PHP 7 won’t support nullable return-types just yet, but there’s an … Read more
First, you should read all about Null Safety in Kotlin which covers the cases thoroughly. In Kotlin, you cannot access a nullable value without being sure it is not null (Checking for null in conditions), or asserting that it is surely not null using the !! sure operator, accessing it with a ?. Safe Call, … Read more
You can either use the “?” operator for a nullable type. public Color? myColor = null; Or use the standard practice for enums that cannot be null by having the FIRST value in the enum (aka 0) be the default value. For example in a case of color None. public Color myColor = Color.None;
The spec (§7.14) says that for conditional expression b ? x : y, there are three possibilities, either x and y both have a type and certain good conditions are met, only one of x and y has a type and certain good conditions are met, or a compile-time error occurs. Here, “certain good conditions” … Read more