enumeration

问题 Closed . This question is opinion-based. It is not currently accepting answers. Want to improve this question? Update the question so it can be answered with facts and citations by editing this post. Closed 5 years ago . What is the difference between (Enumeration, Iterator, Loop) ?? In the following code each example (Enumeration, Iterator, Loop) gets the same output ] but I need to know what is the real difference between them? Is there specific case where i should use one of them and cant

问题 I have a rake file that pulls in data from an external CSV file and enumerates through it with: CSV.foreach(file, :headers => true) do |row| What is the most effective way (in ruby) to specify the starting point within the spreadsheet? :headers => true allows me to start importing from the second line, but what if I want to start a line 20? 回答1: Use .drop(#rows to ignore): CSV.open(file, :headers => true).drop(20).each do |row| 回答2: Ruby enumerators include a drop method that will skip over

问题 Given two IEnumberables of different types, what is the best practice (considering readability and maintainability) for iterating over both lists to perform an action on all possible combinations? My initial solution was to use nested foreach loops, iterating over the first IEnumerable, and then within that loop, iterating over the second IEnumerable and passing the value from the outer and the current loop into the target method. Eg.: enum ParamOne { First, Second, Etc } List<int> paramTwo =

问题 This question already has answers here : What is the difference between <%, <%=, <%# and -%> in ERB in Rails? (7 answers) Closed 4 months ago . I'm using Ruby enumerable to create an array of from another model. The method "companiesattending" class Conference < ActiveRecord::Base has_many :accountconferences has_many :accounts, :through => :accountconferences accepts_nested_attributes_for :accounts def companiesattending accounts.collect {|f| f.name } end end What's strange is when I put

问题 Given are two IEnumerable<A> a and IEnumerable<B> b . It is guaranteed that they are of the same length. I would like to create a new IEnumerable<C> c in which each item c_i is derived using a Func<A, B, C> f by c_i := f (a_i, b_i) . The best I could come up with is manual simultaneous enumeration over both sources and yield-ing the current result, implemented as an extension method. Is there a short way to do it without custom code in .NET >= 4.0? 回答1: You can use Enumerable.Zip. e.g. var c

问题 I have this bit of code here, and at the next statement it's giving me an error saying: List that this enumerator is bound to has been modified. An enumerator can only be used if the list does not change. I really don't know how to further explain this issue, but if you need me to I can try. For Each itemChecked In storedAuthorsListbox.CheckedItems Dim selectedAuthor As String = storedAuthorsListbox.SelectedItem.ToString() Dim authorFile As String = "Authors\" & itemChecked.ToString() Dim

问题 I have a form with about 30 controls on it, and when the user clicks a button, data from each control is saved to a file. But I need to go through every single control on the form (which I can do), but it needs to be in order, For example, I need to start right at the top left of the form and work my way down to the bottom right of the form. Is this how a foreach loop would work? I.e.: foreach(Control control in this.Controls) { } Or does it not go through them in order? 回答1: That would

问题 I'm trying to test if an array of type [Any] contains a value of a specific type (say, Int ). I'm aware that Swift does not know how to compare an Int and a value of arbitrary type, and I guess that's what's being expressed in the autocomplete template: contains(predicate: (protocol<>) throws -> Bool) So I tried this code: let intValue:Int = 5 // for example let isContained = myArrayOfAny.contains({ element in return ((element as? Int) == intValue) }) ...and it compiles (can't make sure it

问题 My textbook barely talks about enumeration in Java, and the videos that I've watched don't explain much. So from what I'm understanding, enumeration is like a whole different class where you can store constants in. Can someone expand to me about the constants and perhaps show me better examples? Like I understand what constants are after seeing the examples such as colors, directions, and in the previous videos it was people, while in the enum version of one my projects during the school year

问题 I found this code that gets an array of files out of a DirectoryInfo : FileInfo[] fileInfoArray = di.EnumerateFiles().Where(f => extensions.Contains(f.Extension.ToLower())).ToArray(); But it only searches the direct children of the path of DirectoryInfo . i.e., it does not include grandchildren. I guess I need to add SearchOption.AllDirectories parameter to somewhere, but where? I tried : di.EnumerateFiles(SearchOption.AllDirectories).Where(f => extensions.Contains(f.Extension.ToLower()))