INQ241B - Day 16 Notes

Web Data

Can use TouchDevelop to open web pages

page main ()
initialize
  do nothing
display
  boxed
    "click me" → post to wall
    box → on tapped(handler)
      where handler() is
        web → browse( "https://www.roanoke.edu/inside" )
      end
    end
  end boxed
end page

But that takes the user out of your app and into another app
Sometimes you just want some of the information on a page

Touch develop can download a web page

page main ()
initialize
  ◳ web page := ""
display
  boxed
    "click me" → post to wall
    box → on tapped(handler)
      where handler() is
        web → download( "https://www.roanoke.edu/inside" )
      end
    end
  end boxed
  ◳ web page → post to wall
end page

But it doesn’t make much sense
What is displayed is the web page’s source code
Can find the text that is displayed among lots of other difficult to decipher text
That additional text specifies how the web looks when it is displayed by the browser
We can get rid of all the parts we don’t want with a little extra work

String Parsing

The web page we downloaded is just one large piece of text

We can extract portions of text

"this is some text" → substring(0, 3) → post to wall

The numbers are the location of the start and the length
Note, it counts from zero
But we don’t always know exactly where the text we want is located

We can search for text to find it

"this is some text" → index of("some", 0)  → post to wall

The number is where to start from when searching
If there is more than one occurance, it finds the first

So we can use this to find what’s for lunch

page main ()
initialize
  ◳ web page := web → download("https://www.roanoke.edu/inside")
  var start := web page → index of("Next Meal:", 0)
  var end := web page → index of("</h4>", start)
  var length := end - start
  ◳ next meal := ◳ web page → substring(start, length)
display
  ◳ next meal → post to wall
end page

Can also join pieces of text together

◳ next meal := "Result: " ∥ ◳ next meal

Activity

Activity 16