In dart I can create an object and call a method in two ways:
First one:
ClassA a = ClassA();
a.methodA();
Second one:
classA().methodA();
Does it have any negative effect to keep doing this? Let's say I want to call 4-5 methods from ClassA in another class, would it have any negative effects, f.x. on performance by using the second way?
That's still the exact same object creation process, it's just a simple constructor call. The only difference is that in one case you're giving the result a name (a), in the other you're not.
It's not like you're saving memory by not saving the object to a variable. In either case, a reference to your new ClassA object needs to exist somewhere, (whether explicitly named or not), otherwise how would methodA know which object to operate on?
However, there is a difference between:
ClassA a = new ClassA()
a.methodA()
a.methodB()
a.methodC()
a.methodD()
a.methodE()
versus
new ClassA().methodA()
new ClassA().methodB()
new ClassA().methodC()
new ClassA().methodD()
new ClassA().methodE()
In the first case, you're reusing the same object a (from a single constructor call) as a target of all 5 instance method calls. In the latter case, you have 5 distinct objects (from 5 separate constructor calls), each as a target of a single method call. These can obviously have very different semantics.