PHP解释器模式的一个简单示例分享
<?php // 解释器模式 abstract class Expression { private static $keyCount = 0; private $key = NULL; abstract function interpret(InterpreterContext $ctx); /** * as array key * @return auto increment value */ public function getKey() { if(!isset($this->key)) { self::$keyCount++; $this->key = self::$keyCount; } return $this->key; } } /** * context */ class InterpreterContext { private $expressionstore = array(); /** * store value */ public function replace(Expression $exp, $value) { $this->expressionstore[$exp->getKey()] = $value; } /** * find value */ public function lookup(Expression $exp) { return $this->expressionstore[$exp->getKey()]; } } /** * literal expression */ class LiteralExpression extends Expression { private $value; public function construct($value) { $this->value = $value; } public function interpret(InterpreterContext $ctx) { $ctx->replace($this, $this->value); } } /** * var=value expression */ class VariableExpression extends Expression { private $name; private $val; public function construct($name, $val=null) { $this->name = $name; $this->val = $val; } public function interpret(InterpreterContext $ctx) { if(!is_null($this->val)) { $ctx->replace($this, $this->val); $this->val = null; } } public function setValue($value) { $this->val = $value; } /** * @override */ public function getKey() { return $this->name; } } abstract class OperatorExpression extends Expression { protected $l_op; protected $r_op; public function construct(Expression $l, Expression $r) { $this->l_op = $l; $this->r_op = $r; } /** * @param $ctx InterpreterContext * @param $result_l Expression $l's result * @param $result_r Expression $r's result */ protected abstract function doInterpret(InterpreterContext $ctx, $result_l, $result_r); public function interpret(InterpreterContext $ctx) { $this->l_op->interpret($ctx); $this->r_op->interpret($ctx); $result_l = $ctx->lookup($this->l_op); $result_r = $ctx->lookup($this->r_op); $this->doInterpret($ctx, $result_l, $result_r); } } /** * equals */ class EqualsExpression extends OperatorExpression { protected function doInterpret(InterpreterContext $ctx, $result_l, $result_r) { $ctx->replace($this, $result_l == $result_r); } } /** * or */ class BooleanOrExpression extends OperatorExpression { protected function doInterpret(InterpreterContext $ctx, $result_l, $result_r) { $ctx->replace($this, $result_l || $result_r); } } /** * and */ class BooleanAndExpression extends OperatorExpression { protected function doInterpret(InterpreterContext $ctx, $result_l, $result_r) { $ctx->replace($this, $result_l && $result_r); } } /** * not */ class BooleanNotExpression extends Expression { private $expr; public function construct(Expression $e) { $this->expr = $e; } public function interpret(InterpreterContext $ctx) { $this->expr->interpret($ctx); $ctx->replace($this, !$ctx->lookup($this->expr)); } } // test code /* $ctx = new InterpreterContext(); $literarl = new LiteralExpression('four'); $literarl->interpret($ctx); // echo $ctx->lookup($literarl); $variable = new VariableExpression('input', '444'); $variable->interpret($ctx); // echo $ctx->lookup($variable); $answer = new VariableExpression('input'); $answer->interpret($ctx); echo $ctx->lookup($answer); */ // $input equas four or $input equals 4 $ctx = new InterpreterContext(); $input = new VariableExpression('input'); $statement = new BooleanOrExpression( new EqualsExpression($input, new LiteralExpression('four')), new EqualsExpression($input, new LiteralExpression(4)) ); $input->setValue('four'); $statement->interpret($ctx); var_dump($ctx->lookup($statement)); // true $input->setValue(4); $statement->interpret($ctx); var_dump($ctx->lookup($statement)); // true $input->setValue(42); $statement->interpret($ctx); var_dump($ctx->lookup($statement)); // false $not = new BooleanNotExpression($statement); // true $not->interpret($ctx); var_dump( $ctx->lookup($not) );
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