Java interface like Predicate, but without an argument
You’re looking for BooleanSupplier. https://docs.oracle.com/javase/8/docs/api/java/util/function/BooleanSupplier.html
predicate
Why do C++ classes without member variables occupy space?
It’s necessary to satisfy an invariant from the C++ standard: every C++ object of the same type needs to have a unique address to be identifiable. If objects took up no space, then items in an array would share the same address.
How to convert an Expression to a Predicate
Func<T, bool> func = expression.Compile(); Predicate<T> pred = t => func(t); Edit: per the comments we have a better answer for the second line: Predicate<T> pred = func.Invoke;
How to apply multiple predicates to a java.util.Stream?
If you have a Collection<Predicate<T>> filters you can always create a single predicate out of it using the process called reduction: Predicate<T> pred=filters.stream().reduce(Predicate::and).orElse(x->true); or Predicate<T> pred=filters.stream().reduce(Predicate::or).orElse(x->false); depending on how you want to combine the filters. If the fallback for an empty predicate collection specified in the orElse call fulfills the identity role (which x->true does … Read more
List.RemoveAll – How to create an appropriate Predicate
The RemoveAll() methods accept a Predicate<T> delegate (until here nothing new). A predicate points to a method that simply returns true or false. Of course, the RemoveAll will remove from the collection all the T instances that return True with the predicate applied. C# 3.0 lets the developer use several methods to pass a predicate … Read more
How to make Selenium wait until an element is present?
You need to call ignoring with an exception to ignore while the WebDriver will wait. FluentWait<WebDriver> fluentWait = new FluentWait<>(driver) .withTimeout(30, TimeUnit.SECONDS) .pollingEvery(200, TimeUnit.MILLISECONDS) .ignoring(NoSuchElementException.class); See the documentation of FluentWait for more information. But beware that this condition is already implemented in ExpectedConditions, so you should use: WebElement element = (new WebDriverWait(driver, 10)) .until(ExpectedConditions.elementToBeClickable(By.id(“someid”))); *Fewer … Read more
C# Linq Where(expression).FirstorDefault() vs .FirstOrDefault(expression)
Either is fine. They both run lazily – if the source list has a million items, but the tenth item matches then both will only iterate 10 items from the source. Performance should be almost identical and any difference would be totally insignificant.
Using Predicate in Swift
This is really just a syntax switch. OK, so we have this method call: [NSPredicate predicateWithFormat:@”name contains[c] %@”, searchText]; In Swift, constructors skip the “blahWith…” part and just use the class name as a function and then go straight to the arguments, so [NSPredicate predicateWithFormat: …] would become NSPredicate(format: …). (For another example, [NSArray arrayWithObject: … Read more
How to write a BOOL predicate in Core Data?
From Predicate Programming Guide: You specify and test for equality of Boolean values as illustrated in the following examples: NSPredicate *newPredicate = [NSPredicate predicateWithFormat:@”anAttribute == %@”, [NSNumber numberWithBool:aBool]]; NSPredicate *testForTrue = [NSPredicate predicateWithFormat:@”anAttribute == YES”]; You can also check out the Predicate Format String Syntax.
Predicate in Java
I’m assuming you’re talking about com.google.common.base.Predicate<T> from Guava. From the API: Determines a true or false value for a given input. For example, a RegexPredicate might implement Predicate<String>, and return true for any string that matches its given regular expression. This is essentially an OOP abstraction for a boolean test. For example, you may have … Read more