PHP下的異步嘗試四：PHP版的Promise
PHP下的異步嘗試系列
若是你還不太瞭解PHP下的生成器和協程，你能夠根據下面目錄翻閱php
- PHP下的異步嘗試一：初識生成器
- PHP下的異步嘗試二：初識協程
- PHP下的異步嘗試三：協程的PHP版thunkify自動執行器
- PHP下的異步嘗試四：PHP版的Promise
- PHP下的異步嘗試五：PHP版的Promise的繼續完善
Promise 實現
代碼結構
│ │ autoload.php │ │ promise1.php │ │ promise2.php │ │ promise3.php │ │ promise4.php │ │ promise5.php │ │ │ └─classes │ Promise1.php │ Promise2.php │ Promise3.php │ Promise4.php │ Promise5.php │ PromiseState.php
嘗試一 (Promise基礎)
classess/PromiseState.phphtml
final class PromiseState
{
const PENDING = 'pending';
const FULFILLED = 'fulfilled';
const REJECTED = 'rejected';
}
classess/Promise1.phpes6
// 嘗試一
class Promise1
{
private $value;
private $reason;
private $state;
public function __construct(\Closure $func = null)
{
$this->state = PromiseState::PENDING;
$func([$this, 'resolve'], [$this, 'reject']);
}
/**
* 執行回調方法裏的resolve綁定的方法
* @param null $value
*/
public function resolve($value = null)
{
// 回調執行resolve傳參的值，賦值給result
$this->value = $value;
if ($this->state == PromiseState::PENDING) {
$this->state = PromiseState::FULFILLED;
}
}
public function reject($reason = null)
{
// 回調執行resolve傳參的值，賦值給result
$this->reason = $reason;
if ($this->state == PromiseState::PENDING) {
$this->state = PromiseState::REJECTED;
}
}
public function getState()
{
return $this->state;
}
public function getValue()
{
return $this->value;
}
public function getReason()
{
return $this->reason;
}
}
promise1.phpsegmentfault
require "autoload.php";
$promise = new Promise1(function($resolve, $reject) {
$resolve("打印我");
});
var_dump($promise->getState());
var_dump($promise->getValue());
結果：
string(9) "fulfilled" string(9) "打印我"
結論或問題：
咱們在這裏建構了最基礎的Promise模型
嘗試二 (增長鏈式then)
classess/Promise2.php數組
<?php
// 嘗試二 （增長鏈式then）
class Promise2
{
private $value;
private $reason;
private $state;
public function __construct(\Closure $func = null)
{
$this->state = PromiseState::PENDING;
$func([$this, 'resolve'], [$this, 'reject']);
}
public function then(\Closure $onFulfilled = null, \Closure $onRejected = null)
{
// 若是狀態是fulfilled，直接回調執行並傳參value
if ($this->state == PromiseState::FULFILLED) {
$onFulfilled($this->value);
}
// 若是狀態是rejected，直接回調執行並傳參reason
if ($this->state == PromiseState::REJECTED) {
$onRejected($this->reason);
}
// 返回對象自身，實現鏈式調用
return $this;
}
/**
* 執行回調方法裏的resolve綁定的方法
* 本狀態只能從pending->fulfilled
* @param null $value
*/
public function resolve($value = null)
{
if ($this->state == PromiseState::PENDING) {
$this->state = PromiseState::FULFILLED;
$this->value = $value;
}
}
/**
* 執行回調方法裏的rejected綁定的方法
* 本狀態只能從pending->rejected
* @param null $reason
*/
public function reject($reason = null)
{
if ($this->state == PromiseState::PENDING) {
$this->state = PromiseState::REJECTED;
$this->reason = $reason;
}
}
public function getState()
{
return $this->state;
}
public function getValue()
{
return $this->value;
}
public function getReason()
{
return $this->reason;
}
}
promise2.phppromise
<?php
require "autoload.php";
$promise = new Promise2(function($resolve, $reject) {
$resolve("打印我");
});
$promise->then(function ($value) {
var_dump($value);
}, function ($reason) {
var_dump($reason);
})->then(function ($value) {
var_dump($value);
}, function ($reason) {
var_dump($reason);
});
結果：
string(9) "打印我" string(9) "打印我"
結論或問題：
咱們實現了鏈式then方法 若是咱們的構造裏的回調是異步執行的話，那麼狀態在沒有變成fulfilled以前，咱們then裏的回調方法就永遠無法執行
嘗試三（真正的鏈式then）
classess/Promise3.php異步
// 解決思路：咱們確定要把then傳入的回調，放到Promise構造裏回調代碼執行完後resolve調用後改變了state狀態後再調用，因此咱們必須存儲到一個地方並方便後續調用
// 咱們須要改造then、resolve和reject方法
class Promise3
{
private $value;
private $reason;
private $state;
private $fulfilledCallbacks = [];
private $rejectedCallbacks = [];
public function __construct(\Closure $func = null)
{
$this->state = PromiseState::PENDING;
$func([$this, 'resolve'], [$this, 'reject']);
}
public function then(\Closure $onFulfilled = null, \Closure $onRejected = null)
{
// 若是是異步回調，狀態未變化以前，then的回調方法壓入相應的數組方便後續調用
if ($this->state == PromiseState::PENDING) {
$this->fulfilledCallbacks[] = static function() use ($onFulfilled, $value){
$onFulfilled($this->value);
};
$this->rejectedCallbacks[] = static function() use ($onRejected, $reason){
$onRejected($this->reason);
};
}
// 若是狀態是fulfilled，直接回調執行並傳參value
if ($this->state == PromiseState::FULFILLED) {
$onFulfilled($this->value);
}
// 若是狀態是rejected，直接回調執行並傳參reason
if ($this->state == PromiseState::REJECTED) {
$onRejected($this->reason);
}
// 返回對象自身，實現鏈式調用
return $this;
}
/**
* 執行回調方法裏的resolve綁定的方法
* 本狀態只能從pending->fulfilled
* @param null $value
*/
public function resolve($value = null)
{
if ($this->state == PromiseState::PENDING) {
$this->state = PromiseState::FULFILLED;
$this->value = $value;
array_walk($this->fulfilledCallbacks, function ($callback) {
$callback();
});
}
}
/**
* 執行回調方法裏的rejected綁定的方法
* 本狀態只能從pending->rejected
* @param null $reason
*/
public function reject($reason = null)
{
if ($this->state == PromiseState::PENDING) {
$this->state = PromiseState::REJECTED;
$this->reason = $reason;
}
}
public function getState()
{
return $this->state;
}
public function getValue()
{
return $this->value;
}
public function getReason()
{
return $this->reason;
}
}
promise3.phpui
require "autoload.php";
$promise = new Promise3(function($resolve, $reject) {
$resolve("打印我");
});
$promise->then(function ($value) {
var_dump($value);
}, function ($reason) {
var_dump($reason);
})->then(function ($value) {
var_dump($value);
}, function ($reason) {
var_dump($reason);
});
結果：
string(9) "打印我" string(9) "打印我"
結論或問題：
咱們此次基本實現了真正的鏈式then方法 不過在Promise/A+裏規範，要求then返回每次都要求是一個新的Promise對象 then方法成功執行，至關於返回一個實例一個Promise回調裏執行resolve方法，resolve值爲then裏return的值 then方法執行失敗或出錯，至關於返回一個實例一個Promise回調裏執行rejected方法，rejected值爲then裏return的值
嘗試四（then返回pormise對象, 並傳遞上一次的結果給下一個Promise對象）
classess/Promise4.phpthis
class Promise4
{
private $value;
private $reason;
private $state;
private $fulfilledCallbacks = [];
private $rejectedCallbacks = [];
public function __construct(\Closure $func = null)
{
$this->state = PromiseState::PENDING;
$func([$this, 'resolve'], [$this, 'reject']);
}
public function then(\Closure $onFulfilled = null, \Closure $onRejected = null)
{
$thenPromise = new Promise4(function ($reslove, $reject) use (&$thenPromise, $onFulfilled, $onRejected) {
//$this 表明的當前的Promise對象，不要混淆了
// 若是是異步回調，狀態未變化以前，then的回調方法壓入相應的數組方便後續調用
if ($this->state == PromiseState::PENDING) {
$this->fulfilledCallbacks[] = static function() use ($thenPromise, $onFulfilled, $reslove, $reject){
$value = $onFulfilled($this->value);
$this->resolvePromise($thenPromise, $value, $reslove, $reject);
};
$this->rejectedCallbacks[] = static function() use ($thenPromise, $onRejected, $reslove, $reject){
$reason = $onRejected($this->reason);
$this->resolvePromise($thenPromise, $reason, $reslove, $reject);
};
}
// 若是狀態是fulfilled，直接回調執行並傳參value
if ($this->state == PromiseState::FULFILLED) {
$value = $onFulfilled($this->value);
$this->resolvePromise($thenPromise, $value, $reslove, $reject);
}
// 若是狀態是rejected，直接回調執行並傳參reason
if ($this->state == PromiseState::REJECTED) {
$reason = $onRejected($this->reason);
$this->resolvePromise($thenPromise, $reason, $reslove, $reject);
}
});
// 返回對象自身，實現鏈式調用
return $thenPromise;
}
/**
* 解決Pormise鏈式then傳遞
* 可參考 [Promises/A+]2.3 [https://promisesaplus.com/#the-promise-resolution-procedure]
* @param $thenPromise
* @param $x $x爲thenable對象
* @param $resolve
* @param $reject
*/
private function resolvePromise($thenPromise, $x, $resolve, $reject)
{
$called = false;
if ($thenPromise === $x) {
return $reject(new \Exception('循環引用'));
}
if ( is_object($x) && method_exists($x, 'then')) {
$resolveCb = function ($value) use($thenPromise, $resolve, $reject, $called) {
if ($called) return ;
$called = true;
// 成功值y有可能仍是promise或者是具備then方法等，再次resolvePromise，直到成功值爲基本類型或者非thenable
$this->resolvePromise($thenPromise, $value, $resolve, $reject);
};
$rejectCb = function($reason) use($thenPromise, $resolve, $reject, $called) {
if ($called) return ;
$called = true;
$reject($reason);
};
call_user_func_array([$x, 'then'], [$resolveCb, $rejectCb]);
} else {
if ($called) return ;
$called = true;
$resolve($x);
}
}
/**
* 執行回調方法裏的resolve綁定的方法
* 本狀態只能從pending->fulfilled
* @param null $value
*/
public function resolve($value = null)
{
if ($this->state == PromiseState::PENDING) {
$this->state = PromiseState::FULFILLED;
$this->value = $value;
array_walk($this->fulfilledCallbacks, function ($callback) {
$callback();
});
}
}
/**
* 執行回調方法裏的rejected綁定的方法
* 本狀態只能從pending->rejected
* @param null $reason
*/
public function reject($reason = null)
{
if ($this->state == PromiseState::PENDING) {
$this->state = PromiseState::REJECTED;
$this->reason = $reason;
}
}
public function getState()
{
return $this->state;
}
public function getValue()
{
return $this->value;
}
public function getReason()
{
return $this->reason;
}
}
promise4.phpcode
require "autoload.php";
$promise1 = new Promise4(function($resolve, $reject) {
$resolve("打印我");
});
$promise2 = $promise1->then(function ($value) {
var_dump($value);
return "promise2";
}, function ($reason) {
var_dump($reason);
});
$promise3 = $promise2->then(function ($value) {
var_dump($value);
return new Promise4(function($resolve, $reject) {
$resolve("promise3");
});
}, function ($reason) {
var_dump($reason);
});
$promise4 = $promise3->then(function ($value) {
var_dump($value);
return "promise4";
}, function ($reason) {
var_dump($reason);
});
var_dump($promise4);
結果：
string(9) "打印我"
string(8) "promise2"
string(8) "promise3"
object(Promise4)#15 (5) {
["value":"Promise4":private]=>
string(8) "promise4"
["reason":"Promise4":private]=>
NULL
["state":"Promise4":private]=>
string(9) "fulfilled"
["fulfilledCallbacks":"Promise4":private]=>
array(0) {
}
["rejectedCallbacks":"Promise4":private]=>
array(0) {
}
}
結論或問題：
一個基本的Pormise，不過咱們上面都是基於成功fulfilled狀態的實現 下面咱們來增長錯誤捕獲
嘗試五（錯誤捕獲）
classess/Promise5.php
class Promise5
{
private $value;
private $reason;
private $state;
private $fulfilledCallbacks = [];
private $rejectedCallbacks = [];
public function __construct(\Closure $func = null)
{
$this->state = PromiseState::PENDING;
$func([$this, 'resolve'], [$this, 'reject']);
}
public function then(\Closure $onFulfilled = null, \Closure $onRejected = null)
{
// 此處做用是兼容then方法的如下四種參數變化，catchError就是第二種狀況
// 1. then($onFulfilled, null)
// 2. then(null, $onRejected)
// 3. then(null, null)
// 4. then($onFulfilled, $onRejected)
$onFulfilled = is_callable($onFulfilled) ? $onFulfilled : function ($value) {return $value;};
$onRejected = is_callable($onRejected) ? $onRejected : function ($reason) {throw $reason;};
$thenPromise = new Promise5(function ($reslove, $reject) use (&$thenPromise, $onFulfilled, $onRejected) {
//$this 表明的當前的Promise對象，不要混淆了
// 若是是異步回調，狀態未變化以前，then的回調方法壓入相應的數組方便後續調用
if ($this->state == PromiseState::PENDING) {
$this->fulfilledCallbacks[] = static function() use ($thenPromise, $onFulfilled, $reslove, $reject){
try {
$value = $onFulfilled($this->value);
$this->resolvePromise($thenPromise, $value, $reslove, $reject);
} catch (\Exception $e) {
$reject($e);
}
};
$this->rejectedCallbacks[] = static function() use ($thenPromise, $onRejected, $reslove, $reject){
try {
$reason = $onRejected($this->reason);
$this->resolvePromise($thenPromise, $reason, $reslove, $reject);
} catch (\Exception $e) {
$reject($e);
}
};
}
// 若是狀態是fulfilled，直接回調執行並傳參value
if ($this->state == PromiseState::FULFILLED) {
try {
$value = $onFulfilled($this->value);
$this->resolvePromise($thenPromise, $value, $reslove, $reject);
} catch (\Exception $e) {
$reject($e);
}
}
// 若是狀態是rejected，直接回調執行並傳參reason
if ($this->state == PromiseState::REJECTED) {
try {
$reason = $onRejected($this->reason);
$this->resolvePromise($thenPromise, $reason, $reslove, $reject);
} catch (\Exception $e) {
$reject($e);
}
}
});
// 返回對象自身，實現鏈式調用
return $thenPromise;
}
public function catchError($onRejected)
{
return $this->then(null, $onRejected);
}
/**
* 解決Pormise鏈式then傳遞
* 可參考 [Promises/A+]2.3 [https://promisesaplus.com/#the-promise-resolution-procedure]
* @param $thenPromise
* @param $x $x爲thenable對象
* @param $resolve
* @param $reject
*/
private function resolvePromise($thenPromise, $x, $resolve, $reject)
{
$called = false;
if ($thenPromise === $x) {
return $reject(new \Exception('循環引用'));
}
if ( is_object($x) && method_exists($x, 'then')) {
try {
$resolveCb = function ($value) use ($thenPromise, $resolve, $reject, $called) {
if ($called) return;
$called = true;
// 成功值y有可能仍是promise或者是具備then方法等，再次resolvePromise，直到成功值爲基本類型或者非thenable
$this->resolvePromise($thenPromise, $value, $resolve, $reject);
};
$rejectCb = function ($reason) use ($thenPromise, $resolve, $reject, $called) {
if ($called) return;
$called = true;
$reject($reason);
};
call_user_func_array([$x, 'then'], [$resolveCb, $rejectCb]);
} catch (\Exception $e) {
if ($called) return ;
$called = true;
$reject($e);
}
} else {
if ($called) return ;
$called = true;
$resolve($x);
}
}
/**
* 執行回調方法裏的resolve綁定的方法
* 本狀態只能從pending->fulfilled
* @param null $value
*/
public function resolve($value = null)
{
if ($this->state == PromiseState::PENDING) {
$this->state = PromiseState::FULFILLED;
$this->value = $value;
array_walk($this->fulfilledCallbacks, function ($callback) {
$callback(); //由於回調自己攜帶了做用於，因此直接調用，沒法參數
});
}
}
/**
* 執行回調方法裏的rejected綁定的方法
* 本狀態只能從pending->rejected
* @param null $reason
*/
public function reject($reason = null)
{
if ($this->state == PromiseState::PENDING) {
$this->state = PromiseState::REJECTED;
$this->reason = $reason;
array_walk($this->rejectedCallbacks, function ($callback) {
$callback(); //由於回調自己攜帶了做用於，因此直接調用，沒法參數
});
}
}
public function getState()
{
return $this->state;
}
public function getValue()
{
return $this->value;
}
public function getReason()
{
return $this->reason;
}
}
promise5.php
require "autoload.php";
$promise1 = new Promise5(function($resolve, $reject) {
$resolve("打印我");
});
$promise2 = $promise1->then(function ($value) {
var_dump($value);
throw new \Exception("promise2 error");
return "promise2";
}, function ($reason) {
var_dump($reason->getMessage());
return "promise3 error return";
});
//咱們能夠簡寫then方法，只傳入$onFulfilled方法，而後錯誤會本身冒泡方式到下一個catchError或then裏處理。
//$promise3 = $promise2->then(function ($value) {
// var_dump($value);
// return new Promise5(function($resolve, $reject) {
// $resolve("promise3");
// });
//})->catchError(function ($reason) {
// var_dump($reason->getMessage());
// return "promise3 error return";
//});
$promise3 = $promise2->then(function ($value) {
var_dump($value);
return new Promise5(function($resolve, $reject) {
$resolve("promise3");
});
}, function ($reason) {
var_dump($reason->getMessage());
return "promise3 error return";
});
$promise4 = $promise3->then(function ($value) {
var_dump($value);
return "promise4";
}, function ($reason) {
echo $reason->getMessage();
});
var_dump($promise4);
結果：
string(9) "打印我"
string(14) "promise2 error"
string(21) "promise3 error return"
object(Promise4)#10 (5) {
["value":"Promise4":private]=>
string(8) "promise4"
["reason":"Promise4":private]=>
NULL
["state":"Promise4":private]=>
string(9) "fulfilled"
["fulfilledCallbacks":"Promise4":private]=>
array(0) {
}
["rejectedCallbacks":"Promise4":private]=>
array(0) {
}
}
結論或問題：
這裏咱們基礎實現了一個能夠用於生產環境的Promise 後續咱們會接續完善這個Promise的特有方法，好比：finally, all, race, resolve, reject等 後續再介紹用Promise實現的自動執行器等
附錄參考
相關文章
- 1. PHP下的異步嘗試三：協程的PHP版thunkify自動執行器
- 2. PHP下的異步嘗試一：初識生成器
- 3. PHP下的異步嘗試二：初識協程
- 4. PHP下的Oauth2.0嘗試 - OpenID Connect
- 5. socket與異步—異步（php版）
- 6. PHP異步編程，異步的本質
- 7. PHP異步---fsockopen
- 8. php 異步fsockopen
- 9. php的異步請求
- 10. php異步處理
- 更多相關文章...
- • MySQL的版本以及版本號 - MySQL教程
- • PHP 7 異常 - PHP 7 新特性
- • 適用於PHP初學者的學習線路和建議
- • PHP開發工具
相關標籤/搜索
每日一句
-
每一个你不满意的现在，都有一个你没有努力的曾经。
最新文章
- 1. 跳槽面試的幾個實用小技巧，不妨看看！
- 2. Mac實用技巧 |如何使用Mac系統中自帶的預覽工具將圖片變成黑白色?
- 3. Mac實用技巧 |如何使用Mac系統中自帶的預覽工具將圖片變成黑白色?
- 4. 如何使用Mac系統中自帶的預覽工具將圖片變成黑白色?
- 5. Mac OS非兼容Windows軟件運行解決方案——「以VMware & Microsoft Access爲例「
- 6. 封裝 pyinstaller -F -i b.ico excel.py
- 7. 數據庫作業三ER圖待完善
- 8. nvm安裝使用低版本node.js(非命令安裝)
- 9. 如何快速轉換圖片格式
- 10. 將表格內容分條轉換爲若干文檔
歡迎關注本站公眾號,獲取更多信息
相關文章