c++ - Is there a design patter that can deal with method call dependencies? -


my problem this:

when design c++ class, in cases, methods can called after other methods have been called, or after data member has been prepared.

i found quite hard deal when there data member dependencies not obvious, , class needs extended support more features , functionalities. error-prone.

execution speed of code not important in case, code clarity/maintainability/sensibility more important.

if method2 called after method1 class has state. want keep state consistent , methods change/use state should not damage state.

so need incapsulation. incapsulation not how make field private , create setfield() method change state. right answer: object change state. if have setters every single field have unprotected object , control consistent state has leaked.

in practice, re-desing code data set during previous steps only. in case don't worry checking "is data prepared?" each time method2 called.

to avoid untimely calls there several approaches. each has pro , contras. suppose have chain of state0 -> method1 -> state1 -> method2 -> state2 -> method3 -> state3

  • throw exception if object has different state. f.e. inside method1 add if currentstate.differs(state0) throw exception easy implement, way won't in terms of understanding , maintaining project

  • use combination of state , chain-of-responsibility pattern. divide class in several ones , each accept previous 1 input param , return next class in chain. f.e. class0 have method wih signature class1 method1(state0), class1 have class2 method2(class1) , class 2 have state3 method3(class2). nobody call class2.method3 or method1(class3) - not compile. side effect lot of classes. rigid process flow more flexible next option.

  • use template pattern. create processor class process method , make sure class call desired methods. state3 process(state0) { preparestuff(); state1 = method1(state0) somepreparation(state1) state2 = method2(state1) anotherprepare(state2) return method3(state2) } alter process flow subclassing processor , overriding preparation methods. nobody override process(). disadvantage always whole process , can't stop after method2 (in fact can lead leak state , again uncontrolable process) note policy template

in sense both ways incapsulate state of process @ higher level.

there ways implement call dependency. no matter choose have strictly limit possibility call methods anywhere @ random moment.


Comments

Post a Comment

Popular posts from this blog

Is there a better way to structure post methods in Class Based Views -

i'm using class based views in django , never specify url in ajax calls , omit action parameter in form because know these requests go through post method of class based view. notice view - profile page make many requests depending on user updating on page - post method become convoluted , if/else mess example: def post(self, request, *args, **kwargs): # handle user changing available date if request.post.get('availabledate') != none: self.updateavailabledate(request) return jsonresponse({'result':'success'}) if request.post.get('newprojectname') != none: creative_user = creativeuserprofile.objects.get(id = request.user.id) project = project.create_project(creative_user, request.post['newprojectname']) project.save() return jsonresponse({'projectid': project.id }) if request.post.get('projectimage') != none , request.files['file']: proj
Read more

performance - Why is XCHG reg, reg a 3 micro-op instruction on modern Intel architectures? -

i'm doing micro-optimization on performance critical part of code , came across sequence of instructions (in at&t syntax): add %rax, %rbx mov %rdx, %rax mov %rbx, %rdx i thought had use case xchg allow me shave instruction , write: add %rbx, %rax xchg %rax, %rdx however, dimay found agner fog's instruction tables , xchg 3 micro-op instruction 2 cycle latency on sandy bridge, ivy bridge, broadwell, haswell , skylake. 3 whole micro-ops , 2 cycles of latency! 3 micro-ops throws off 4-1-1-1 cadence , 2 cycle latency makes worse original in best case since last 2 instructions in original might execute in parallel. now... cpu might breaking instruction micro-ops equivalent to: mov %rax, %tmp mov %rdx, %rax mov %tmp, %rdx where tmp anonymous internal register , suppose last 2 micro-ops run in parallel latency 2 cycles. given register renaming occurs on these micro-architectures, though, doesn't make sense me done way. why wouldn't register renamer
Read more

jquery - Responsive Navbar with Sub Navbar -

good day, forgive me nav vocabulary not best. if question confusing apologize. i'm working on navigation bar needs centered on page @ 768px , above. items in nav open (or perhaps toggle) subnav lives directly below. these nav should appear centered on page. i have been able work through responsive portion of nav bar, having main items align vertically , sub nav menu of each item roll out below, , gave them indent separation. working well. however, issue not responsive side, behavior @ width greater 768px. happens toggling menu's sub navigation pushes other main items down page below sub nav. here's code: $(document).ready(function () { //stick in fixed 100% height behind navbar don't wrap $('#slide-nav.navbar-inverse').after($('<div class="inverse" id="navbar-height-col"></div>')); $('#slide-nav.navbar-default').after($('<div id="navbar-height-col"></d
Read more