closures
Unexpected Non-Void Return Value In Void Function (Swift 2.0)
You have a problem because your line: return minions does not return from your function. Instead, it returns from the completion handler in dataTaskWithRequest. And it shouldn’t be doing so because that closure is a void function. The problem which you have results from the fact that dataTaskWithRequest is an asynchronous operation. Which means that … Read more
Read/Write Python Closures
To expand on Ignacio’s answer: def counter(): count = 0 def c(): nonlocal count count += 1 return count return c x = counter() print([x(),x(),x()]) gives [1,2,3] in Python 3; invocations of counter() give independent counters. Other solutions – especially using itertools/yield are more idiomatic.
How do closures infer their type based on the trait they’re required to implement?
It seems to be a glitch. The Rust-analyzer LSP is able to infer what the type is supposed to be, but for whatever reason the compiler can’t. From what I can tell, this code doesn’t compile on any version of Rust, and cannot be automatically fixed with cargo fix. Interestingly, the compiler does seem to … Read more
is it possible to create a generic closure in Swift? [duplicate]
No, because variables and expressions can’t be generic. There are only generic functions and generic types. To clarify: In some languages you can have types with a universal quantifier, like forall a. a -> a. But in Swift, types cannot have a universal quantifier. So expressions and values cannot be themselves generic. Function declarations and … Read more
Javascript Closures and ‘this’
WHen the function is called, “this” refers to row. If you want to have the object, you can do it something like this: ] AddChildRowEvents: function(row, p2) { var theObj = this; if(document.attachEvent) { row.attachEvent(‘onclick’, function(){theObj.DoSomething();}); } else { row.addEventListener(‘click’, function(){theObj.DoSomething();}, false); } }, When the function is called, it has access to the variable … Read more
What is a closure? Does java have closures? [duplicate]
A closure is a first class function with bound variables. Roughly that means that: You can pass the closure as a parameter to other functions The closure stores the value of some variables from the lexical scope that existed at the time that is was created Java initially didn’t have syntactic support for closures (these … Read more
How to mock nested functions?
for example you need to mock nested function calls (chained functions) from Google DRIVE API result = get_drive_service().files().insert(body=’body’, convert=True).execute() so you need to patch through functions: service_mock(), files(), insert(), till last execute() response: from mock import patch with patch(‘path.to.import.get_drive_service’) as service_mock: service_mock.return_value.files.return_value.insert.\ return_value.execute.return_value = {‘key’: ‘value’, ‘status’: 200} Main scheme: first.return_value.second.return_value.third.return_value.last.return_value = rsp
JavaScript: Why does closure only happen if I assign the return function to a variable?
_counter is the local variable within function counter(). Every time when you call counter() a new _counter will be created. But var createClosure = counter() only called the function 1 time, that’s why _counter is not newly created every time and ‘remembered’ there (that’s where closure happens)
When to use closure? [closed]
Closures are simply great tools. When to use them? Any time you like… As has already been said, the alternative is to write a class; for example, pre C# 2.0, creating a parameterised thread was a real struggle. With C# 2.0 you don’t even need the `ParameterizedThreadStart’ you just do: string name = // blah … Read more