Next iteration in `each` loop

Next iteration in `each` loop

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I have a collection:

@monday = HomeTask.where(:class_room => current_user.class_room, :day => 'Понеділок').order(created_at: :desc)

The @monday variable contains data from the database. In view, I show all dates from the collection:

<% @monday.each_with_index do |mnd, i| %>
  <% if mnd.data == mnd.data[i + 1] %>
    <%= link_to 'nice' %>
  <% else %>
    <%= link_to 'ohhh...' %>
  <% end %>
<% end %>

Within if body, I want to refer to the next element. But it does not work. In C++, to refer to the next element in the first iteration, it would be coded like this:

if(array[i] == array[i+1])

How do I use each in Ruby?


If you want to iterate an array and have access to more than one item in each iteration you can use each_cons

arr = [1,2,3,4,5,6,7,8]
arr.each_cons(2){|a,b| 
   puts "#{a} : #{b}"
}
# 1 : 2
# 2 : 3
# 3 : 4
# 4 : 5
# 5 : 6
# 6 : 7
# 7 : 8

Using each_cons you can easily compare two (or more) consecutive items of an array.

Next iteration in `each` loop, If you want to iterate an array and have access to more than one item in each iteration you can use each_cons arr = [1,2,3,4,5,6,7,8]  Each iteration of the For Each loop calls the iterator. When a Yield statement is reached in the iterator, the expression in the Yield statement is returned, and the current location in code is retained. Execution is restarted from that location the next time that the iterator is called. The following example uses an iterator function.


arr = [1,2,3,4,5,6,7,8]

enum = arr.to_enum
  #=> #<Enumerator: [1, 2, 3, 4, 5, 6, 7, 8]:each>    
loop { puts "%d : %d" % [enum.next, enum.peek] }
1 : 2
2 : 3
3 : 4
4 : 5
5 : 6
6 : 7
7 : 8

See Kernel#to_enum1, Kernel#loop, Enumerator#next and Enumerator#peek. peek raises a StopIteration exception when it is executed after the last element of arr has been generated. loop handles that exception by breaking out of the loop.

1. As to why this Kernel instance method is documented as an Object instance method, please see the second paragraph at the docs for Object.

JavaScript continue Statement, The continue statement breaks one iteration (in the loop) if a specified condition occurs, and continues with the next iteration in the loop. Note: The continue statement (with or without a label reference) can only be used inside a loop. For loop usage in Swift. The for loop might be the most well-known method for iteration over all programming languages. It’s also known as the for-in loop in Swift. For-In loop with collections. This example iterates over an array of cities, also known as a collection in Swift.


What if you could go with following changes,

-  <% if mnd.data == mnd.data[i + 1] %>
+  <% if @monday[i+1] != nil && mnd.data == @monday[i+1].data %>

Or simply,

-  <% if mnd.data == mnd.data[i + 1] %>
+  <% if mnd.data == @monday[i+1].try(:data) %>

Skip inside the for each loop - General - Discussions, Skip inside the for each loop forEach expression return an empty set ( "{}" ) when a particular iteration is not a match, then only the matching entries will  Calls next() repeatedly to obtain each item from the iterator in turn; Terminates the loop when next() raises the StopIteration exception; The loop body is executed once for each item next() returns, with loop variable i set to the given item for each iteration. This sequence of events is summarized in the following diagram:


continue - Manual, continue is used within looping structures to skip the rest of the current loop If a switch is inside a loop, continue 2 will continue with the next iteration of the  With each iteration, the loop increments n and adds that value to x. Therefore, x and n take on the following values: After the first pass: n = 1 and x = 1; After the second pass: n = 2 and x = 3; After the third pass: n = 3 and x = 6; After completing the third pass, the condition n < 3 is no longer true, so the loop terminates. Example 2. Avoid infinite loops.


Loops in Ruby, Execution continued to the next iteration of the loop. break and What this method does is loop through each element in our array, in order, starting from '​Bob' . continue passes control to the next iteration of a for or while loop. It skips any remaining statements in the body of the loop for the current iteration. The program continues execution from the next iteration. continue applies only to the body of the loop where it is called.


Pass control to next iteration of for or while loop, The program continues execution from the next iteration. continue applies only to the body of the loop where it is called. In nested loops, continue skips remaining​  The present solution produces the same flow as your OP. It does not use Labels, but this was not a requirement of the OP. You only asked for "a simple conditional loop that will go to the next iteration if a condition is true", and since this is cleaner to read, it is likely a better option than that using a Label.