Tutorial by Examples: defer

Variables of character type or of a derived type with length parameter may have the length parameter either assumed or deferred. The character variable name character(len=len) name is of length len throughout execution. Conversely the length specifier may be either character(len=*) ... ! Ass...

A defer statement in Go is simply a function call marked to be executed at a later time. Defer statement is an ordinary function call prefixed by the keyword defer. defer someFunction() A deferred function is executed once the function that contains the defer statement returns. Actual call to th...

Deferred function calls serve a similar purpose to things like finally blocks in languages like Java: they ensure that some function will be executed when the outer function returns, regardless of if an error occurred or which return statement was hit in cases with multiple returns. This is useful f...

Some LINQ methods return a query object. This object does not hold the results of the query; instead, it has all the information needed to generate those results: var list = new List<int>() {1, 2, 3, 4, 5}; var query = list.Select(x => { Console.Write($"{x} "); return ...

We can use $q to defer operations to the future while having a pending promise object at the present, by using $q.defer we create a promise that will either resolve or reject in the future. This method is not equivalent of using the $q constructor, as we use $q.defer to promisify an existing routin...

A defer statement consists of a block of code, which will be executed when a function returns and should be used for cleanup. As Swift's guard statements encourage a style of early return, many possible paths for a return may exist. A defer statement provides cleanup code, which then does not need ...

When using a defer-statement, make sure the code remains readable and the execution order remains clear. For example, the following use of the defer-statement makes the execution order and the function of the code hard to comprehend. postfix func ++ (inout value: Int) -> Int { defer { value...

Deferred execution enables combining different operations to build the final query, before evaluating the values: var list = new List<int>() {1,1,2,3,5,8}; var query = list.Select(x => x + 1); If we execute the query at this point: foreach (var x in query) { Console.Write($"...

With deferred execution, if the data to be queried is changed, the query object uses the data at the time of execution, not at the time of definition. var data = new List<int>() {2, 4, 6, 8}; var query = data.Select(x => x * x); If we execute the query at this point with an immediate m...

We can use the unit type as a function argument to define functions that we don't want executed until later. This is often useful in asynchronous background tasks, when the main thread may want trigger some predefined functionality of the background thread, like maybe moving it to a new file, or if...

Avoid this Anti-Pattern var myDeferred = $q.defer(); $http(config).then(function(res) { myDeferred.resolve(res); }, function(error) { myDeferred.reject(error); }); return myDeferred.promise; There is no need to manufacture a promise with $q.defer as the $http service alread...

This code implements a version of std::async, but it behaves as if async were always called with the deferred launch policy. This function also does not have async's special future behavior; the returned future can be destroyed without ever acquiring its value. template<typename F> auto asyn...

When creating a std::unique_lock, there are three different locking strategies to choose from: std::try_to_lock, std::defer_lock and std::adopt_lock std::try_to_lock allows for trying a lock without blocking: { std::atomic_int temp {0}; std::mutex _mutex; std::thread t( [&...