the last hash in param in a function call can omit {}_Ruby_编程开发_程序员俱乐部

there is one note about the element order in hashes:

Ruby 1.9 actually guarantees that hashes keep their elements in the same order entered, but it would be unwise ever to count on a particular ordering.?

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let's see this method:

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stylesheet_link_tag 'blueprint/screen', :media => 'screen'

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you will find the last param is a hash, but why there is no {} around this hash?

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the reason is this:

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when the hash is the last argument in a function call, the {} is optional, the following two lines are equivalent:

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stylesheet_link_tag 'blueprint/screen', { :media => 'screen' }
stylesheet_link_tag 'blueprint/screen', :media => 'screen'

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note this only apply to a function call, not a function definition.

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by the way, the html generated by the above code is:

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<link href="/stylesheets/blueprint/screen.css" media="screen" rel="stylesheet"
type="text/css" />
<link href="/stylesheets/blueprint/print.css" media="print" rel="stylesheet"
type="text/css" />