如何在Ruby中检查参数“param [：some_value]”

I know some ways to check if parameter is not nil

我知道一些检查参数是否为零的方法

if param[:some_value]
if param[:some_value].present?
if !param[:some_value].nil?    #unless param[:some_value].nil? 
if !param[:some_value].blank?  #unless param[:some_value].blank?

Which one is correct and most popular? What is the difference between them? I'd rather use if param[:some_value] because it is simplest and shorterst.

哪一个是正确的,最受欢迎的?它们之间有什么区别?我宁愿使用if param [:some_value],因为它最简单,最短。

4 个解决方案

#1

Here are some differences between nil?, blank? and present?:

以下是nil?之间的一些区别,空白?和礼物?:

>> "".nil?
=> false
>> "".blank?
=> true
>> "".present?
=> false
>> " ".nil?
=> false
>> " ".blank?
=> true
>> " ".present?
=> false

Note that present? translates to not nil and not blank. Also note that while nil? is provided by Ruby, blank? and present? are helpers provided by Rails.

请注意礼物?转换为不是零而不是空白。还要注意,虽然没有?由Ruby提供,空白?和礼物?是Rails提供的帮手。

So, which one to choose? It depends on what you want, of course, but when evaluating params[:some_value], you will usually want to check not only that it is not nil, but also if it is an empty string. Both of these are covered by present?.

那么,选择哪一个?当然,这取决于你想要什么,但是在评估params [:some_value]时,你通常不仅要检查它不是nil,还要检查它是否为空字符串。这两个都被现在覆盖?

#2

The relevant cases are:

#3

if param[:some_value] is the most common one.

如果param [:some_value]是最常见的。

But if you're working with boolean data (true,false) the best method would be if !param[:some_value].nil?, because:

但是如果你使用布尔数据(true,false),最好的方法是if!param [:some_value] .nil ?,因为:

>> hash = {foo:false, bar:nil}

>> !! hash[:foo]
=> false
>> !! hash[:bar]
=> false

>> !! !hash[:foo].nil?
=> true
>> !! !hash[:bar].nil?
=> false

(!! returns the boolean value, which would be tested in an if-statement)

(!!返回布尔值,将在if语句中测试)

Also it could be important to test if the value is really nil, or if the key-value combo isn't defined. key?(key) does that for you.

此外,测试值是否为零或者未定义键值组合可能很重要。键(键)为你做的。

>> hash ={foo:nil}

>> hash[:foo]
=> nil
>> hash[:not_there]
=> nil

>> hash.key?(:foo)
=> true
>> hash.key?(:not_there)
=> false

#4

It depends what you want to do, but I generally use these forms:

这取决于你想做什么,但我通常使用这些形式:

if param[:some_value]
  ...
end

# and
param[:some_value] && something
# or
param[:some_value] || somethinn

Of course all of them only work if the parameter can't be false. In that case I'd go for the unless param[:some_value].nil? version.

当然,只有参数不能为假时,它们才有效。在那种情况下,我会去除非参数[:some_value] .nil?版。

#1