ruby-on-rails - 更改包含特定字符串的所有数组元素

Question

array = ["Spam is bad", "Ham is good"]

我想从数组中选择包含单词“good”的元素，并将字符串设置为新变量。我怎么能这样做？

Answer 1

由于目前为止这两个答案都没有指导您如何将数组中的字符串更新为新值，因此这里有一些选项:

# Find every string matching a criteria and change them
array.select{ |s| s.include? "good" }.each{ |s| s.replace( "bad" ) }

# Find every string matching a pattern and change them
array.grep.replace( "bad" ).each{ |s| s.replace( "bad" ) }

# Find the first string matching a criteria and change it
array.find{ |s| s =~ /good/ }.replace( "bad" )

但是，以上所有内容都会更改字符串的每个实例。例如:

jon   = Person.new "Johnny B. Goode"
array = [ jon.name, "cat" ]
array.find{ |s| s =~ /good/i }.replace( "bad" )

p array #=> "bad"
p jon   #=> #<Person name="bad">  Uh oh...

如果你不想要这种副作用——如果你想用一个不同的字符串替换数组中的字符串，而不是改变字符串本身——那么您需要找到项目的索引并更新它:

# Find the _first_ index matching some criteria and change it
array[ array.index{ |s| s =~ /good/ } ] = "bad"

# Update _every_ item in the array matching some criteria    
array[i] = "bad" while i = array.index{ |s| s =~ /good/i }

# Another way to do the above
# Possibly more efficient for very large arrays any many items
indices = array.map.with_index{ |s,i| s =~ /good/ ? i : nil }.compact
indices.each{ |i| array[i] = "bad" }

最后，最简单也是最快速的，不涉及索引:

# Create a new array with the new values
new_array = array.map do |s|
  if s =~ /good/i  # matches "Good" or "good" in the string
    "bad"
  else
    s
  end
end

# Same thing, but shorter syntax
new_array = array.map{ |s| s =~ /good/i ? "bad" : s }

# Or, change the array in place to the new values
new_array = array.map!{ |s| s =~ /good/i ? "bad" : s }