6. Required hash argument
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| class HTML
def self.div(attrs)
attrs = attrs.map{|k,v| "#{k}='#{v}'" }.join(' ')
"<div #{attrs}></div>"
end
end
HTML.div # ArgumentError
HTML.div({:id => 'body'}) # >> "<div id="body"></div>"
HTML.div({:class => 'red', :id => 'body'}) # >> "<div class="red" id="body"></div>"
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Well, the {...} isn’t necessary when dealing with hash argument as
the only or last argument, thus the above can be rewritten as:
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| HTML.div(:id => 'body') # >> "<div id="body"></div>"
HTML.div(:class => 'red', :id => 'body') # >> "<div class="red" id="body"></div>"
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And using the newer (1.9) json-like hash, we can again rewrite the above as:
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| HTML.div(id: 'body') # >> "<div id="body"></div>"
HTML.div(class: 'red', id: 'body') # >> "<div class="red" id="body"></div>"
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7. Optional hash argument
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| class HTML
def self.div(attrs = {})
attrs = attrs.map{|k,v| "#{k}='#{v}'" }.join(' ')
"<div #{attrs}></div>"
end
end
HTML.div # >> "<div ></div>"
HTML.div(id: 'body') # >> "<div id="body"></div>"
HTML.div(class: 'red', id: 'body') # >> "<div class="red" id="body"></div>"
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Let’s say we want id attribute to be always present, & when unspecified,
we auto-generate one:
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| class HTML
class << self
def div(attrs = {})
attrs[:id] ||= "div-#{count}"
attrs = attrs.map{|k,v| "#{k}='#{v}'" }.join(' ')
"<div #{attrs}></div>"
end
def count
@count ||= 0
@count += 1
end
end
end
HTML.div(id: 'body') # >> "<div id="body"></div>"
HTML.div(class: 'red') # >> "<div class="red" id="div-1"></div>"
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8. Mixed arguments with last as optional hash
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| class HTML
class << self
def element(tag, attrs = {})
attrs[:id] ||= "#{tag}-#{count}"
attrs = attrs.map{|k,v| "#{k}='#{v}'" }.join(' ')
"<#{tag} #{attrs}></#{tag}>"
end
def count
@count ||= 0
@count += 1
end
end
end
HTML.element # >> ArgumentError
HTML.element('div') # >> "<div id="div-1"></div>"
HTML.element('div', {id: 'body'}) # >> "<div id="body"></div>"
HTML.element('div', {class: 'red'}) # >> "<div class="red" id="div-2"></div>"
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Again, the {...} isn’t necessary when dealing with hash argument as
the only or last argument, thus the above can be rewritten as:
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| HTML.element('div', id: 'body') # >> "<div id="body"></div>"
HTML.element('div', class: 'red') # >> "<div class="red" id="div-3"></div>"
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