在Ruby中,有什么方法可以过滤包含"time"一词的对象的所有方法？

Question

我尝试了以下内容,部分工作:

>> s.methods.map {|n| n if n =~ /time/}
=> [nil, nil, nil, nil, nil, nil, nil, nil, "skip_time_zone_conversion_for_attri
butes", nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, ni
l, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, ni
l, "timestamped_migrations", nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, n
il, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, n
il, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, n
il, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, n
il, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, "time_zone_aware
_attributes", nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, n
il, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, "default_timezone", nil, n
il, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, n
il, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, n
il, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, n
il, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, "recor
d_timestamps", nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil,
nil, nil, nil, nil, nil, nil, nil]

>> s.methods.each {|n| p n if n =~ /time/}
"skip_time_zone_conversion_for_attributes"
"timestamped_migrations"
"time_zone_aware_attributes"
"default_timezone"
"record_timestamps"
=> ["extended_by", "before_create", "vote_ids=", "save_without_dirty", "_delete"
, "touch", "daemonize", "after_destroy", "skip_time_zone_conversion_for_attribut
es", "methods", "send", "to_query", "becomes", "after_validation", "store_full_s
ti_class?", "save_with_transactions!", "autosave_associated_records_for_votes",
"require_library_or_gem", "enum_for", "taint", "instance_variable_defined?", "ac
     [...] and the rest of the whole array

>> s.methods.filter {|n| n =~ /time/}
NoMethodError: undefined method `filter' for #<Array:0x4de6b00>
        from (irb):93

Answer 1

grep 是实现这个目标的另一种简单方法:

1.9.0 > require 'date'
 => true 
1.9.0 > x = Date.new
 => #<Date: -1/2,0,2299161> 
1.9.0 > x.methods.grep /time/
 => ["ctime", "asctime", "strftime"] 

使用您尝试的方法:

map将给定的块应用于给定枚举的每个元素,返回一个新的可枚举.这不是你想要的(正如你所看到的).

methods.each一些作品,但显然只是打印出结果并不是非常有用.它根本不像Ruby,但你可以做到:

matching_methods = []
s.methods.each {|m| matching_methods << m if m =~ /time/}

累积匹配/time/到matching_methods数组中的每个方法.当然,如果你这样做,那么

s.methods.select { |m| m =~ /time/ }

是优选的.

最后,filterRuby中不存在; 这就是select(或find_all)的用途.