How to create an Array of objects like the below C++ example?
What's the Ruby way of doing Print print[1000];?
The below code is C++. I'm just wondering if Ruby has an option to instantiate 1000 unique objects of a class:
class Print
{
public:
Print()
{
static int count = 0;
cout<<"h"<<++count<<endl;
}
};
int main()
{
Print print[1000];
getchar();
return 0;
}
To get 1000 copies of a string instantiated, we can do this:
collection_of_strings = Array.new(1000, String.new('h'))
print collection_of_strings
This is the same object stored in the array. And then that array printed.
This form of Array.new with the block given will create an individually instantiated object, however many times you gave for the argument:
>> collection = Array.new(10) {String.new}
=> ["", "", "", "", "", "", "", "", "", ""]
And the proof by checking object_id of each object in the array.
>> collection.each {|e| puts e.object_id}
85621980
85621970
85621960
85621950
85621940
85621930
85621920
85621910
85621900
85621890
=> ["", "", "", "", "", "", "", "", "", ""]
Given that
"I suppose count is a global variable and the output looks like: "h0 h1 h2 h3 "
The following should work (see Array#new block for details [1]). It doesn't require an external variable, the block is passed the array's index:
Array.new(1000) {|count| "h#{count}"}
to put them all in one string, try:
Array.new(1000) {|count| "h#{count}"}.join(' ')
Alternate to ThomasW's answer:
output = []
1000.times do |i| { output << "h#{i}" }
Yes there is! In translating your C++ to Ruby, this is what I come up with:
#create dummy class
class Kraken
# equivalent to your C++ static variable which I think
# should be declared outside the constructor
@@count = 0
# increment the count class variable on every
def initialize
@@count = @@count + 1
end
end
# Release the Kraken!
kraken = Array.new(1000) { Kraken.new }
Array.new(1000){Kraken.new} should do fine
Array.new(1000){Kraken.new} contains an implicit loop (specifically, in MRI, for (i=0; i<len; i++) { rb_ary_store(ary, i, rb_yield(LONG2NUM(i))); ARY_SET_LEN(ary, i + 1); }). There is no way to do this in Ruby (or any other language) without a loop of some sort, just like the C++ code will invoke the constructor 1000 times when compiled to machine code.To get that output with Ruby you can just do: puts (0..999).to_a.
Or, if you want the 'h's you can do: (0..999).each {|n| puts "h#{n}"}
C++? Interesting if its notcountis a global variable and the output looks like: "h0 h1 h2 h3 "... ?C++, notRuby. You are looking at the wrong code if itsRubyyou want to work with