design patterns - Difference between Business Delegate and View Helper -

-

they seem same thing - seperate presentation tier logic complexities of business tier. difference?

both try separate complexities of components, but:

  • view helper's intent make views lighter (make them display stuff, really);
  • business delegate intends decouple 2 components (leaving details of plumbing work third 1 in between them).

i can see confusion comes from, alike in way. but, in practice, address 2 different issues:

view helper

as systems grow, people tend start putting code on view, jsp, , begins more , more complex. views aren't supposed have lot of code. supposed display data. if put heavy calculation in jsp, instance, on 1 hand code hidden amongst html tags and, on other, can't reuse anywhere in system. imagine having maintenance in code this. you'd go crazy.

view helper teaches way can avoid making views simpler through creation of helper class heavy work , make jsp call instead of keeping complex code inside jsp.

business delegate

when have component, mycalculator, calls external component (say ejb weatherejb) changes lot, end having change component lot too.

think of mycalculator, instance, important class of system, you'll not want change time. if break else? if changing @ branch?

besides, you'll want change mycalculator when your business change, not everytime else changes.

you'll see getting crazier when mycalculator calls ten other components. you'll changing everyday!

business delegate comes rescue advising: add class weatherdelegate can perform calls weatherejb , make mycalculator use instead of calling weatherejb directly.

this way, everytime weatherejb changes, don't need change mycalculator. you'll need edit weatherdelegate accordingly. (also, if someday wish change way weather a, say, web service, once again, you'd have edit weatherdelegate.)

in end...

...they both say: create work you. view helper says don't unecessary work on view; , business delegate tells decouple components, system's responsibilities better distributed. both make system easier maintain.


Comments

Post a Comment

Popular posts from this blog

Perl - how to grep a block of text from a file -

-
it can in xml or text format. how in general grep block of text in perl? <track type="ws"> <range> <rangestart>0</rangestart> <rangeend>146.912</rangeend> <locationindex>0</locationindex> <propertyindex>0</propertyindex> </range> </track> <track type="ps" id="1"> <range> <rangestart>0</rangestart> <rangeend>146.912</rangeend> <locationindex>1</locationindex> <propertyindex>1</propertyindex> </range> </track> i want grep type="ps" , till </range> . one solution open file, read line line , match block. open(fh, "file.txt"); foreach $line (<fh>) { if ($line =~ m/type="cc"(.*?)<\/range>/) { print $1; } } but there more optimal solution without reading file line l
Read more

delphi - How to remove all the grips on a coolbar if I have several coolbands? -

-
Image
if set mycoolbar.fixedorder true,only grip on first band hidden. well,if use delphi 7 create vcl forms application,then put coolbar on , create 3 coolbans hold other controls,only grip , top coolbands can hidden setting mycoolbar.fixedorder:=true. i've uploaded picture make things clear. you got fixedorder property wrong. fixed property not allow bands rearranged if set true . setting property of coolbar true keep user changing bands order @ runtime, user can still move , resize bands. can give advice can do, actual solution problem, well, have wait answer. my advice use 3 coolbars in row , setting "fixedorder" property true , bandborderstyle bsnone . way grip hidden on of them. about property, it's not bug of ide, actual preference of property.
Read more

javascript - Animating array of divs; only the final element is modified -

-
this baffling me @ moment. i'm experienced programmer looking throw bit of surprise fiancee on countdown page our wedding. desired effect simulated confetti falling behind main page. setup follows: i have array of divs in javascript. each div absolutely positioned on page. have interval set updates every 50 or milliseconds. on each tick, run loop on array of divs, , calculations , update positions. problem problem having, however, though can see divs created, stored array, , modified (in case, each has slight randomized rotation) during initialization phase, once tick update position starts, div stored in whatever last slot of array gets position updated. tried hard-coding each div index testing purposes, strictly last element update position. upon printing current "left" , "top" style values each div before , after calculations shows value has been changed, no visible change noticeable. here's basic code: javascript var container;
Read more