Ruby keywords yield

Ruby keywords yield

The ruby keyword yield is a commonly used keyword in actual programming. Programmers who have just learned the ruby language must first master the usage of this type of basic keywords.

Some basic keywords in ruby are essential for beginners. Here we will take a look at the distinctive Ruby keyword yield.

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Input

1. Def call_block
2. Puts "Start of method"
3. Yield
4. Yield
5. Puts "End of method"
6. End
7. Call_block {puts "in the block "}

Output:

Start of Method

In the block

In the block

End of Method

The usage of yield is different from that on the Internet. Some are placeholders, some are "Give way", and some are macros.

Http://www.javaeye.com/topic/31752

Http://axgle.javaeye.com/blog/31018

In my opinion, the. NET developer is more willing to regard it as a method delegate, which can be written in. net.

Input

 
 

  
  
Delegate outhandler ();
  
  
Void call_block (outhandler yield)
  
  
{
  
  
Console. writeline ("Start of method ");
  
  
Yield ();
  
  
Yield ();
  
  
Console. writeline ("End of method ");
  
  
}
  
  
Void test () {console. writeline
("In the block ");}
  
  
// Call
  
  
Call_block (test );
 
 

Haha, the above Code seems to be much more redundant than Ruby, but it is also much more rigorous. I don't know if my analysis is correct, but it cannot be completely replaced, if the function defines a variable:

 
 

  
  
def call_block   
  
  
puts "Start of method"   
  
  
@count=1   
  
  
yield   
  
  
yield   
  
  
puts "End of method"   
  
  
end   
  
  
call_block { puts @count=@count+1 }  
 
 

Output:

Start of Method

2

3

End of Method

That is to say, this proxy needs to obtain access to the context scope. NET may not be implemented. This is a bit like a macro, or even code weaving. However, it seems that macros cannot be passed through methods. Because of this, Ruby's yield is quite distinctive. Let's take a look at some of his examples:

Input

 
 

  
  
[ 'cat', 'dog', 'horse' ].each
 {|name| print name, " " }   
  
  
5.times { print "*" }   
  
  
3.upto(6) {|i| print i }   
  
  
('a'..'e').each {|char| print char }  
 
 

Output:

Cat dog horse ***** 3456 ABCDE

Hey, you can handle all these implementations of. Net delegation, and give a function pointer...

From: http://developer.51cto.com/art/200912/170864.htm