Ruby-on-rails 是否有等同于 PHP 的 isset() 的 Rails？
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Is there a Rails equivalent to PHP's isset()?
提问by keybored
Basically just a check to make sure a url param was set. How I'd do it in PHP:
基本上只是检查以确保设置了 url 参数。我将如何在 PHP 中做到这一点：
if(isset($_POST['foo']) && isset($_POST['bar'])){}
Is this the rough/best equivalent to isset() in RoR?
这是 RoR 中 isset() 的粗略/最佳等价物吗？
if(!params['foo'].nil? && !params['bar'].nil?) end
回答by Simone Carletti
The closer match is probably #present?
更接近的比赛可能是 #present?
# returns true if not nil and not blank
params['foo'].present?
There are also a few other methods
还有一些其他的方法
# returns true if nil
params['foo'].nil?
# returns true if nil or empty
params['foo'].blank?
回答by Andrew
You can also use defined?
你也可以使用 defined?
See example from: http://www.tutorialspoint.com/ruby/ruby_operators.htm
请参阅以下示例：http: //www.tutorialspoint.com/ruby/ruby_operators.htm
foo = 42
defined? foo # => "local-variable"
defined? $_ # => "global-variable"
defined? bar # => nil (undefined)
Many more examples at the linked page.
链接页面上的更多示例。
回答by Jacob Relkin
Yes. .nil?is the equivalent of isset()in that casewhen checking the existence of a key in a Hash.
是的。.nil?相当于isset()在那种情况下检查 a 中的键是否存在Hash。
You should use Hash's key?method, which returns trueif the given key is present in the receiver:
你应该使用Hash'skey?方法，true如果给定的键存在于接收器中，它会返回：
if(params.key?('foo') && params.key?('bar')) end
回答by BitOfUniverse
I think the most important thing, when you migrating from PHP to ROR, is the understanding of the fact that in Ruby everything is true except false and nil
我认为最重要的事情是，当你从 PHP 迁移到 ROR 时，要理解这样一个事实：在 Ruby 中，除了 false 和 nil 之外，一切都是真的
So, your code:
所以，你的代码：
if(!params['foo'].nil? && !params['bar'].nil?){}
if(!params['foo'].nil? && !params['bar'].nil?){}
is equivalent for:
相当于：
if(params['foo'] && params['bar']) end
if(params['foo'] && params['bar']) end
and this is full equivalent for your PHP code.
这完全等同于您的 PHP 代码。
