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How can I pass a predicate into a method but also have it work if no predicate is passed? I thought maybe something like this, but it doesn't seem to be correct.
private bool NoFilter() { return true; }
private List<thing> GetItems(Predicate<thing> filter = new Predicate<thing>(NoFilter))
{
return rawList.Where(filter).ToList();
}
703
If we want to pass a function that does not return a value, we have to use the Action<> delegate in C#. The Action<T> delegate works just like the function delegate; it is used to define a function with the T parameter. We can use the Action<> delegate to pass a function as a parameter to another function.
Function Call When calling a function with a function parameter, the value passed must be a pointer to a function. Use the function's name (without parentheses) for this: func(print); would call func , passing the print function to it.
Passing and Returning Objects in C++ In C++ we can pass class's objects as arguments and also return them from a function the same way we pass and return other variables.
private List<thing> GetItems(Func<thing, bool> filter = null)
{
return rawList.Where(filter ?? (s => true)).ToList();
}
In this expression s => true is the fallback filter which is evaluated if the argument filter is null. It just takes each entry of the list (as s) and returns true.
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