Bouncer Pattern

http://groovy-lang.org/design-patterns.html#_bouncer_pattern

保鏢模式主要負責對函數的輸入參數的合法性檢查， 如果遇到非法輸出，則停止函數后續執行。

groovy提供了 assert 機制， 語言級別內置功能。

The Bouncer Pattern describes usage of a method whose sole purpose is to either throw an exception (when particular conditions hold) or do nothing. Such methods are often used to defensively guard pre-conditions of a method.

When writing utility methods, you should always guard against faulty input arguments. When writing internal methods, you may be able to ensure that certain pre-conditions always hold by having sufficient unit tests in place. Under such circumstances, you may reduce the desirability to have guards on your methods.

Groovy differs from other languages in that you frequently use the assert method within your methods rather than having a large number of utility checker methods or classes.

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例子

void doStuff(String name, Object value) { assert name != null, 'name should not be null' assert value != null, 'value should not be null' // do stuff }

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或者， 合法性檢查， 檢測出非法性， 主動 拋出異常。

class NumberChecker { static final String NUMBER_PATTERN = "\\\\d+(\\\\.\\\\d+(E-?\\\\d+)?)?" static isNumber(str) { if (!str ==~ NUMBER_PATTERN) { throw new IllegalArgumentException("Argument '$str' must be a number") } } static isNotZero(number) { if (number == 0) { throw new IllegalArgumentException('Argument must not be 0') } } }



def stringDivide(String dividendStr, String divisorStr) { NumberChecker.isNumber(dividendStr) NumberChecker.isNumber(divisorStr) def dividend = dividendStr.toDouble() def divisor = divisorStr.toDouble() NumberChecker.isNotZero(divisor) dividend / divisor } println stringDivide('1.2E2', '3.0') // => 40.0

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轉載于:https://www.cnblogs.com/lightsong/p/8724285.html

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