Your post is correct. Unfortunately, if you need to use an optional parameter at the very end of the parameter list, you have to specify everything up until that last parameter. Generally if you want to mix-and-match, you give them default values of ” or null, and don’t use them inside the function if they … Read more
Not really. The standard way is to use a default value that the user would not be expected to pass, e.g. an object instance: DEFAULT = object() def foo(param=DEFAULT): if param is DEFAULT: … Usually you can just use None as the default value, if it doesn’t make sense as a value the user would … Read more
You are almost always better off using an options hash. def ldap_get(base_dn, filter, options = {}) options[:scope] ||= LDAP::LDAP_SCOPE_SUBTREE … end ldap_get(base_dn, filter, :attrs => X)
One good use case for ‘Optional parameters’ in conjunction with ‘Named Parameters’ in C# 4.0 is that it presents us with an elegant alternative to method overloading where you overload method based on the number of parameters. For example say you want a method foo to be be called/used like so, foo(), foo(1), foo(1,2), foo(1,2, … Read more
A function can have multiple signatures if the signatures differ in arity. You can use that to supply default values. (defn string->integer ([s] (string->integer s 10)) ([s base] (Integer/parseInt s base))) Note that assuming false and nil are both considered non-values, (if (nil? base) 10 base) could be shortened to (if base base 10), or … Read more
You can work around this very easily by changing your signature. void Foo(TimeSpan? span = null) { if (span == null) { span = TimeSpan.FromSeconds(2); } … } I should elaborate – the reason those expressions in your example are not compile-time constants is because at compile time, the compiler can’t simply execute TimeSpan.FromSeconds(2.0) and … Read more
You can declare like this CREATE PROCEDURE MyProcName @Parameter1 INT = 1, @Parameter2 VARCHAR (100) = ‘StringValue’, @Parameter3 VARCHAR (100) = NULL AS /* check for the NULL / default value (indicating nothing was passed */ if (@Parameter3 IS NULL) BEGIN /* whatever code you desire for a missing parameter*/ INSERT INTO …….. END /* … Read more
If you put the declaration in a header file, and the definition in a separate .cpp file, and #include the header from a different .cpp file, you will be able to see the difference. Specifically, suppose: lib.h int Add(int a, int b); lib.cpp int Add(int a, int b = 3) { … } test.cpp #include … Read more
Dynamically changing searches based on the given parameters is a complicated subject and doing it one way over another, even with only a very slight difference, can have massive performance implications. The key is to use an index, ignore compact code, ignore worrying about repeating code, you must make a good query execution plan (use … Read more
Solution You can use new Guid() instead public void Problem(Guid optional = new Guid()) { // when called without parameters this will be true var guidIsEmpty = optional == Guid.Empty; } You can also use default(Guid) default(Guid) also will work exactly as new Guid(). Because Guid is a value type not reference type, so, default(Guid) … Read more