用户输入为空时应该抛出什么异常? [英] What is the exception that should be thrown when user input is blank?

问题描述

我已经搜索了一段时间，但我肯定已经错过了，是否有任何文档说明当值不正确/空白时应该抛出什么?

I've been searching for some time now, and I'm sure I've missed it, is there any documentation that states what should be thrown when a value is incorrect/blank?

例如， Python 具有 ValueError 和文档明确说明了何时使用它.

For example, Python has ValueError and the documentation clearly states when to use it.

我有以下方法:

proc getJobinfo {question} {
    puts -nonewline "$question: "
    flush stdout
    gets stdin answer
    set cleanedanswer [string trim [string totitle $answer]]
    if {$cleanedanswer eq ""} {
       # What error should be thrown?
    }
    return $cleanedanswer
}

我搜索了 throw ， 错误 ，和 catch ，但是找不到它.

I've searched throw, error, and catch, but couldn't find it.

推荐答案

Tcl没有预定义的异常层次结构.throw命令带有2个参数: type 是单词列表；而 message 是人类的错误消息.

Tcl doesn't have a pre-defined hierarchy of exceptions. The throw command takes 2 arguments: type is a list of words; and message is an error message for humans.

您可以做类似的事情

proc getJobinfo {question} {
    ...
    if {$cleanedanswer eq ""} {
        throw {Value Empty} "Please provide a suitable answer."
    } elseif {[string length $cleanedanswer] < 5} {
        throw {Value Invalid} "Your answer is too short."
    } else ...
    return $cleanedanswer
}

如果您想捕获该错误:

try {
    set answer [getJobinfo "What is the answer to this question"]
} trap {Value *} msg {
    puts "Value Error: $msg"
}

---

throw 和 try 通过 throw 调用的 type 字进行交互.我们抛出空值"或无效值".在陷阱中，我们完全匹配 Value ，但是我们不会完全匹配 * .事后看来， * 不应存在. try 联机帮助页一开始不是很清楚:

---

throw and try interact via the type words of the throw call. We throw "Value Empty" or "Value Invalid". In the trap, we match Value exactly, but we won't match * exactly. In hindsight the * should not be there. The try manpage is not super clear at first read:

陷阱 模式 variableList 脚本

如果对 body 的求值导致错误并且解释器的状态词典中的 -errorcode 的前缀等于 pattern <，则此子句匹配/em>.从-错误代码中提取的前缀词的数量等于模式的列表长度，并且在-错误代码和模式进行比较.

This clause matches if the evaluation of body resulted in an error and the prefix of the -errorcode from the interpreter's status dictionary is equal to the pattern. The number of prefix words taken from the -errorcode is equal to the list-length of pattern, and inter-word spaces are normalized in both the -errorcode and pattern before comparison.

模式不是 regexp 或 string match 意义上的模式:它是一个单词列表，每个单词都被一对一地匹配以及尝试 body 中抛出的单词列表.

pattern is not a pattern in the regexp or string match sense: it's a list of words that is matched one-by-one with the list of words thrown in the try body.

try 可以通过多个陷阱实现，以具有级联的陷阱":

The try can be implemented with multiple traps to have cascading "catches":

try {
    set answer [getJobinfo "What is the answer to this question"]

} trap {Value Empty} msg {
    do something specific here

} trap {Value Invalid} msg {
    do something specific here

} trap {Value} msg {
    do something general for some other "throw {Value anything} msg"

} on error e {
    this can be default catch-all for any other error

} finally {
    any cleanup code goes here
}

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