Archive for February, 2006
Ruby: (Dubinski) Kopiraj objekt
Želio sam napraviti objekt. Zatim ga kopirati. Zatim promijeniti kopiju bez mijenjanja izvornika. Ali nisam znao kako. Kad god nešto ne znam, pitam wtr-general listu. Poslao sam pitanje. Pa sam pomislio da bi bilo lijepo kad bi objasnio zašto želim kopirati objekt. Ali, objašnjenje se odužilo, pa sam ga stavio na moj blog.
Dobio sam odgovor. “Probaj Object#clone”. Može li biti tako jednostavno?! Može. Ipak, to je Ruby. Ali ne, nije tako jednostavno. Nije radilo. Izvorni objekt se mijenjao sa svojim duplikatom.
class Page
attr_accessor :texts
def initialize(url, texts)
@url, @texts = url, texts
end
end
page_view = Page.new(“app.com/view.aspx”, ["File > View"])
page_view_after_add = page_view.clone
page_view_after_add.texts < < "File added."
puts page_view.inspect
puts page_view_after_add.inspect
Rezulat:
#<Page:0x2820ae0 @url=”app.com/view.aspx”, @texts=["File > View", "File added."]>
#<Page:0x2820a98 @url=”app.com/view.aspx”, @texts=["File > View", "File added."]>
Ali sad sam znao gdje gledati. Upisao sam “ri Object#clone” i “ri Object#dup” u Command Prompt (čak sam pogledao i na http://www.ruby-doc.org/core/). Kaže (na oba mjesta, i za Object#clone i za Object#dup):
“Proizvodi plitku kopiju objekta – kopiraju se objektove varijable instance (kako ovo prevesti?), ali ne i objekt na kojeg se odnose.”
Dakle, stvara “plitku” kopiju. To mi ne treba. Trebam “pravu” kopiju.
Google mi je pomogao. Potražio sam “ruby copy object” i našao http://www.rubygarden.org/ruby?Make_A_Deep_Copy_Of_An_Object.
Tajna riječ je “dubinsko” kopiranje.
Dodao sam ovo klasi Page (i zamijenio page_view.clone sa page_view.deep_clone) i dobio sam što sam trebao!
def deep_clone
Marshal::load(Marshal.dump(self))
end
Rezulat:
#<Page:0x4c1dd10 @url="app.com/view.aspx", @texts=["File > View"]>
#<Page:0x4c1dc50 @url="app.com/view.aspx", @texts=["File > View", "File added."]>
Ne razumijem kako radi, i nije me briga, sve dok radi.
Watir, Ruby, objekti i varijable
Živim od testiranja web aplikacija. Služim se Rubyjem i Watirom za automatiziranje testova funkcionalnosti. Moje skripte su narasle, pa sam napravio mali framework (ne znam kako ovo pametno prevesti) kako bi ih pojednostavnio (sav kod u ovom članku je pojednostavljen i neisproban).
Klasa Page olakšava provjeravanje url-a i tekst(ov)a stranice.
class Page
def initialize(ie, url, texts)
@ie, @url, @texts = ie, url, texts
end
def check
@texts.each do |text|
assert(@ie.contains_text(text))
end
assert_equal(@url, @ie.url)
end
end
“Pogledaj element” stranica u aplikaciji koju testiram ima tekst (breadcrumb – opet ne znam kako bi ovo smisleno preveo) {vrsta_elementa} > View (primjer: File > View).”
Nakon što je element dodan/promijenjen, na toj stranici se nalazi i tekst {vrsta_elementa} {akcija}. (primjer: File added.).
Klasa File, naravno, testira datoteke.
class File
def initialize
@page_view = Page.new(
"app.com/view.aspx",
["File > View"])
@page_view_after_add = Page.new(
"app.com/view.aspx",
["File > View", "File added."])
@page_view_after_edit = Page.new(
"app.com/view.aspx",
["File > View", "File edited."])
end
def add
# add file
@page_view_after_add.check
end
def edit
# edit file
@page_view_after_edit.check
end
def view
# go to file
@page_view.check
end
end
I sve baš lijepo radi. Sve što trebam napisati je ovo.
file = File.new file.add file.edit file.view
Postoje tri objekta. Jedan za svaku (@page_view…) varijablu. “id” u “Page:{id}” je različit za svaku varijablu.
#<Page:0x2b5ac28 @url="app.com/view.aspx", @texts=["File > View"]>
#<Page:0x2b5ab98 @url="app.com/view.aspx", @texts=["File > View", "File added."]>
#<Page:0x2b5ab08 @url="app.com/view.aspx", @texts=["File > View", "File edited."]>
Ali, dupliciranje me muči.
Želio bi da File#initialize izgleda ovako.
@page_view = @page_view_after_add = @page_view_after_edit = Page.new( "app.com/view.aspx", ["File > View"]) @page_view_after_add.texts < < "File added." @page_view_after_edit.texts << "File edited."
Ali (iznenađenje!), to ne radi. Pa, prilično sam novi u objektno orijentiranom svijetu, pa mi to i nije iznenađenje.
Na ovaj način stvoren je samo jedan Page objekt, i sve tri varijable pokazuju na njega. Bez obzira koju varijablu promijenim, ona promijeni objekt na koji pokazuje. Rezultat je da su sve tri varijable iste. To nije ono što sam želio.
#<Page:0x2820048 @url="app.com/view.aspx", @texts=["File > View", "File added.", "File edited."]>
#<Page:0x2820048 @url="app.com/view.aspx", @texts=["File > View", "File added.", "File edited."]>
#<Page:0x2820048 @url="app.com/view.aspx", @texts=["File > View", "File added.", "File edited."]>
Isprobao sam nekoliko alternativa, ali niti jedna nije uspjela. Za sad mogu živjeti s duplikacijom, ali bi je volio ukloniti iz mojih skripti.
Watir, Ruby, Objects and Variables
I test web applications for living. I use Ruby and Watir for automating functional tests. My scripts have grown, so I made a little framework to make them simpler (all code in this post is simplified and not tested).
Class Page makes checking page url and text(s) easier.
class Page
def initialize(ie, url, texts)
@ie, @url, @texts = ie, url, texts
end
def check
@texts.each do |text|
assert(@ie.contains_text(text))
end
assert_equal(@url, @ie.url)
end
end
View item page at application under test has text (breadcrumb) {item_type} > View (example: File > View).
After item is added/edited, at that page there is also text {item_type} {action}. (example: File added.).
Class File tests files, of course.
class File
def initialize
@page_view = Page.new(
"app.com/view.aspx",
["File > View"])
@page_view_after_add = Page.new(
"app.com/view.aspx",
["File > View", "File added."])
@page_view_after_edit = Page.new(
"app.com/view.aspx",
["File > View", "File edited."])
end
def add
# add file
@page_view_after_add.check
end
def edit
# edit file
@page_view_after_edit.check
end
def view
# go to file
@page_view.check
end
end
And it works just nice. All I have to write is this.
file = File.new file.add file.edit file.view
There are three objects. One for each (@page_view…) variable. “id” in “Page:{id}” is different for each variable.
#<Page:0x2b5ac28 @url="app.com/view.aspx", @texts=["File > View"]>
#<Page:0x2b5ab98 @url="app.com/view.aspx", @texts=["File > View", "File added."]>
#<Page:0x2b5ab08 @url="app.com/view.aspx", @texts=["File > View", "File edited."]>
But, duplication bugs me.
I would like that File#initialize looks like this.
@page_view = @page_view_after_add = @page_view_after_edit = Page.new( "app.com/view.aspx", ["File > View"]) @page_view_after_add.texts < < "File added." @page_view_after_edit.texts << "File edited."
But (surprise!), it does not work. Well, I am pretty new in object oriented world, so this was not really a surprise for me.
This way only one Page object is created, and all three variables point to it. No matter which variable I change, it changes the object it points to. Result is that all three variables are the same. Not what I wanted to do.
#<Page:0x2820048 @url="app.com/view.aspx", @texts=["File > View", "File added.", "File edited."]>
#<Page:0x2820048 @url="app.com/view.aspx", @texts=["File > View", "File added.", "File edited."]>
#<Page:0x2820048 @url="app.com/view.aspx", @texts=["File > View", "File added.", "File edited."]>
I have tried a few alternatives, but none worked. I will live with duplication for now, but I would like to remove it from my scripts.
