hello: can you help me ?we all know that we can use a class'object in main method in java,but how can i use a class'object after designing a class in ruby? i only know i can make an object and use it after having a class,i can also use a class method in a class to get some result after designing a class method.But why i can do that? i do not know the reason? is there an only place like main method of java in which i can use my classes? is there a rule that can guide me to use my ruby class correctly? thank you ! -- Posted via http://www.ruby-forum.com/.
On Jul 26, 6:43 am, Guo Yangguang <gy...@163.com> wrote:
> hello: > can you help me ?we all know that we can use a class'object in main > method in java,but how can i use a class'object after designing a class > in ruby? i only know i can make an object and use it after having a > class,i can also use a class method in a class to get some result after > designing a class method.But why i can do that? i do not know the > reason? is there an only place like main method of java in which i can > use my classes? is there a rule that can guide me to use my ruby class > correctly? > thank you ! > -- > Posted viahttp://www.ruby-forum.com/.
I hope I understand your question correctly.
Ruby is in its essence an interpreter. When you type in your command prompt
>ruby my_script.rb
the interpreter (that by itself is just another application) reads your file line by line and executes every line. Think of every line in Ruby as a command to the interpreter and that the interpreter executes every single line. That means you can use your classes anywhere you like as long as they were defined before. For example, this is absolutely correct in Ruby:
a = "I assign even before any declaration" puts "Moreover I can output its value #{a}"
(1..10).each {|x| puts "#{x} I can do anything I wish"}
class C1 puts "When interpreter will read this he will print. Not very useful but possible" def a() end end
c = C1.new # now we can use our class puts "We can do something in between..."
class C2 puts "We can define another class" def b end end
puts "And so on..."
As you can see it's quite different from Java. If you want to feel more comfortable think of your Ruby code written entirely inside one big 'main' Java function. Just remember - every line is executed!
> hello: > can you help me ?we all know that we can use a class'object in main > method in java,but how can i use a class'object after designing a class > in ruby? i only know i can make an object and use it after having a > class,i can also use a class method in a class to get some result after > designing a class method.But why i can do that? i do not know the > reason? is there an only place like main method of java in which i can > use my classes? is there a rule that can guide me to use my ruby class > correctly?
As has been mentioned already, the body of the script file is what in Java is your "main" method. Arguments are in ARGV, i.e. you can do
ARGV.each do |arg| puts arg end
You can as well read from ARGV - which is a kind of IO that combines all file names on the command line. A simple "cat" replacement looks like this:
thank you very much!Your answer make me understand more about object in ruby.I am very glad.But still ,i have another question.Please read an example following: class Test def initialize e="e" end def Test.say_hello puts "Hello from #{self.name}" puts "hello from #{self.class}" end say_hello end
Your means is we can use a class anyplaces after defining it ,but in this example,i use a classmehod immediately after defining it in class context.This is valid.Can you explain it for me?What is more,if it is a instance method ,i can not get any result.why? thank you !
> Ruby is in its essence an interpreter. When you type in your command > prompt
>>ruby my_script.rb
> the interpreter (that by itself is just another application) reads > your file line by line and executes every line. Think of every line in > Ruby as a command to the interpreter and that the interpreter executes > every single line. That means you can use your classes anywhere you > like as long as they were defined before. For example, this is > absolutely correct in Ruby:
> a = "I assign even before any declaration" > puts "Moreover I can output its value #{a}"
> (1..10).each {|x| puts "#{x} I can do anything I wish"}
> class C1 > puts "When interpreter will read this he will print. Not very > useful but possible" > def a() > end > end
> c = C1.new # now we can use our class > puts "We can do something in between..."
> class C2 > puts "We can define another class" > def b > end > end
> puts "And so on..."
> As you can see it's quite different from Java. If you want to feel > more comfortable think of your Ruby code written entirely inside one > big 'main' Java function. Just remember - every line is executed!
> thank you very much!Your answer make me understand more about object in > ruby.I am very glad.But still ,i have another question.Please read an > example following: > class Test > def initialize > e="e" > end > def Test.say_hello > puts "Hello from #{self.name}" > puts "hello from #{self.class}" > end > say_hello > end
It is not completely clear what you want to achieve but some remarks might be helpful
class Test def initialize e="e" # this code is not realy useful, e is a scope local variable that will be thrown away, you probably want to do this: @e = "e" # this is an instance variable end
> > Ruby is in its essence an interpreter. When you type in your command > > prompt
> >>ruby my_script.rb
> > the interpreter (that by itself is just another application) reads > > your file line by line and executes every line. Think of every line in > > Ruby as a command to the interpreter and that the interpreter executes > > every single line. That means you can use your classes anywhere you > > like as long as they were defined before. For example, this is > > absolutely correct in Ruby:
> > a = "I assign even before any declaration" > > puts "Moreover I can output its value #{a}"
> > (1..10).each {|x| puts "#{x} I can do anything I wish"}
> > class C1 > > puts "When interpreter will read this he will print. Not very > > useful but possible" > > def a() > > end > > end
> > c = C1.new # now we can use our class > > puts "We can do something in between..."
> > class C2 > > puts "We can define another class" > > def b > > end > > end
> > puts "And so on..."
> > As you can see it's quite different from Java. If you want to feel > > more comfortable think of your Ruby code written entirely inside one > > big 'main' Java function. Just remember - every line is executed!
Sorry ,i am not show it very clear.Please read this example again:
class Test def Test.say_hello puts "Hello from #{self.name}" puts "hello from #{self.class}" end say_hello #i don't understand here end
Normally,we can use a class anyplaces after defining it ,but in this example,i use a classmehod immediately after defining it "in class context".This is valid.I means calling a classmethod(not an intance method) in a class defintion--not after defining that class--is valid .Can you explain it for me? thank you !
Robert Dober wrote: > On 7/29/07, Guo Yangguang <gy...@163.com> wrote: >> end >> say_hello >> end
> It is not completely clear what you want to achieve but some remarks > might be helpful
> class Test > def initialize > e="e" # this code is not realy useful, e is a scope local > variable that will be thrown away, you probably want to do this: > @e = "e" # this is an instance variable > end
> attr_accessor :e # for some tests below
> def Test.say_hello > ... > end > say_hello > end
now in Ruby there is always a self defined, the implicit receiver to which unqualified messages are sent Fire up your irb to learn a little bit more about that 536/37 > irb irb(main):001:0> self => main # This is the default self provided by the Ruby Interpreter irb(main):002:0> class Test ### look what happens to self when inside a class statement irb(main):003:1> puts self irb(main):004:1> end Test => nil irb(main):005:0> class Test ### say_hello is sent to self, which is Test in this context irb(main):006:1> say_hello ### but Test does not reply to this message yet irb(main):007:1> end NameError: undefined local variable or method `say_hello' for Test:Class from (irb):6 from :0 irb(main):008:0> class Test ### The def statement defines an *instance* method on self, we have therefore ### to write Test.say_hello in order to tell def a method on Test itself, but you ### seem to know that already :) irb(main):009:1> def Test.say_hello irb(main):010:2> puts "Hello" irb(main):011:2> end irb(main):012:1> end => nil irb(main):013:0> class Test ### self is set to Test again and now Test responds to the #say_hello message irb(main):014:1> say_hello irb(main):015:1> end Hello => nil ### and just to show that the main object was not influenced by what we defined for Test irb(main):020:0> say_hello NameError: undefined local variable or method `say_hello' for main:Object from (irb):20 from :0 irb(main):021:0>
> end
> Normally,we can use a class anyplaces after defining it ,but in this > example,i use a classmehod immediately after defining it "in class > context".This is valid.I means calling a classmethod(not an intance > method) in a class defintion--not after defining that class--is valid > .Can you explain it for me? thank you !
Funny but you explained it quite well, if there were no ? I would say you have made a correct statement. Maybe you are just puzzled by the dynamic nature of Ruby that everything springs into life when executed.
class Test dosomething end
as a matter of fact is equivalent to
Test = Class::new
class Test #(1) doesomething end
meaning that at point (1) Test is a well defined complete Ruby class already :)
> Robert Dober wrote: > > On 7/29/07, Guo Yangguang <gy...@163.com> wrote: > >> end > >> say_hello > >> end
> > It is not completely clear what you want to achieve but some remarks > > might be helpful
> > class Test > > def initialize > > e="e" # this code is not realy useful, e is a scope local > > variable that will be thrown away, you probably want to do this: > > @e = "e" # this is an instance variable > > end
> > attr_accessor :e # for some tests below
> > def Test.say_hello > > ... > > end > > say_hello > > end
> example,i use a classmehod immediately after defining it "in class > context".This is valid.I means calling a classmethod(not an intance > method) in a class defintion--not after defining that class--is valid > .Can you explain it for me? thank you !
> Robert Dober wrote: > > On 7/29/07, Guo Yangguang <gy...@163.com> wrote: > >> end > >> say_hello > >> end
> > It is not completely clear what you want to achieve but some remarks > > might be helpful
> > class Test > > def initialize > > e="e" # this code is not realy useful, e is a scope local > > variable that will be thrown away, you probably want to do this: > > @e = "e" # this is an instance variable > > end
> > attr_accessor :e # for some tests below
> > def Test.say_hello > > ... > > end > > say_hello > > end
OK，i can understand now.Thank you!Thank all the people who helped me.Unlike our Chinese help site,here is so kind to fresher of ruby.I will persuade my friends to come here too.
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