\Co\promise

###API

namespace Co;

function promise(Closure $closure): Promise;

Parameter description

Parameters	Type	Description
$closure	Closure	Entry closure function, run immediately in the current context

Closure parameters

Parameters	Type	Description
$resolve	Closure	Resolve contract
$reject	Closure	Reject future contract

Return value

Returns a Promise object

Overview

Promise (promise/expiration mechanism) is a core concept in the ripple framework and is used to handle asynchronous operations. A Promise object represents the final completion or failure of an asynchronous operation, as well as its result value. Compared with Future, Promise provides a more intuitive API that is easier to understand and use.

Usage

Use this method to create a Promise object

$promise = \Co\promise(Closure $callback): Promise

ripple will provide two parameters for the closure function you submit, one is the resolve callback function and the other is the reject callback function. Use these two callback functions to resolve or reject a futures contract.

$promise = \Co\promise(function ($resolve, $reject) {
    $resolve('success'); // Resolve a future contract
    
    // $reject('error'); // Reject a futures contract
    
    //TODO: More actions...
});

Promise status

A Promise object has three states:

• pending: initial state, neither success nor failure state. -fulfilled: means the operation was completed successfully.
• rejected: means the operation failed.

A Promise object can only be converted from the pending state to the fulfilled or rejected state. Once converted to fulfilled or rejected state, it cannot be converted to other states again.

$promise = \Co\promise(function ($resolve, $reject) {
    //TODO: Asynchronous operations such as reading files/network requests/database queries...

    $resolve('success'); // Resolve a future contract
});

// When the future contract is resolved, the callback function in the then method will be triggered.
$promise->then(function (mixed $result) {
    echo $value;
});

// When the futures contract is rejected, the callback function in the catch method will be triggered.
$promise->catch(function (Exception $e) {
    echo $reason;
});

$promise->await(); // Wait for the promise to be resolved

Notes

resolve and reject will only change the state and result of Promise and will not prevent subsequent code execution.