objective c - How to creating an immutable object along with a Builder pattern in ObjC? -


what struggling creating immutable object builder pattern in objc. have user object following properties:

  1. first name
  2. last name

to ensure immutability propose following code: 

@protocol user @property (nonatomic, strong, readonly) nsstring *const firstname; @property (nonatomic, strong, readonly) nsstring *const lastname; @end  @interface user: nsobject<user> - (instancetype)initwithfirstname:(nsstring *)fname withlastname:(nsstring *)lname; @end  @implementation user @synthesize firstname; @synthesize lastname;  - (instancetype)initwithfirstname:(nsstring *)fname withlastname:(nsstring *)lname {     nsparameterassert(fname);     nsparameterassert(lname);     if (self = [super init]) {         self->firstname = [fname copy];         self->lastname = [lname copy];     }     return self; } @end

what struggling how implement builder immutable object?

helpful links on builder:

the builder pattern in objc

builder pattern definiton

the link posted above uses 2 objects implement builder pattern. dedicated builder object subsequently passed create/build method returning object built. here contrived example of implement builder pattern immutable object.

first let's create immutable object; object built builder object.

@interface person: nsobject  @property (nonatomic, readonly) nsstring *firstname; @property (nonatomic, readonly) nsstring *lastname;  @end  @implementation person  - (instancetype)initwithfirstname:(nsstring *)firstname lastname:(nsstring *)lastname{       self = [super init]      if(!self) return nil;       _firstname = [firstname copy];      _lastname = [lastname copy];       return self;  }  @end

now let's create builder object.

@interface personbuilder: nsobject  @property (nonatomic, strong) nsstring *firstname;  @property (nonatomic, strong) nsstring *lastname;  - (person *)create;  @end  @implementation personbuilder  - (person *)create{       return [[person alloc] initwithfirstname:self.firstname lastname:self.lastname];  }  @end

implement classes

personbuilder *builder = [personbuilder new]; builder.firstname = "john"; builder.lastname = "doe";  person *john = [builder create];

in objective-c don't see reason implement builder pattern unless trying avoid long , confusing constructor signature or if object has 2 many properties or options such nsdatecomponent. builder pattern allows split initialization of complex immutable object multiple simple setter calls. create/build method implemented on builder gives hook point in can verify object being created want. use pattern in rare cases.


Comments

Post a Comment

Popular posts from this blog

searchKeyword not working in AngularJS filter -

i writing app using angularjs on front end. want search through table word/field; 1 search box everything. according article here: http://hello-angularjs.appspot.com/searchtable can use filter: searchkeyword this. this code, , not working expected. <label>search: <input ng-model="searchkeyword"></label> <table ng-repeat="post in posts | orderby: sort | filter: searchkeyword"> <tr> <td> {{index(post)}} </td> <td> {{post.title}} </td> <td> {{post.author}} </td> <td> {{post.content}} </td> <td> {{post.date | date: "d/m/yyyy"}} </td> </tr> </table> what should do? thank you try this: controller $scope.posts = [ {title:'title one', author:'author one', content: 'content one'}, {title:'title two', author:'author two', content: 'cont...
Read more

sequelize.js - Sequelize: sort by enum cases -

i have model ( article ) field (the name type ) of type enum('source', 'translated') , return 1 article ordered type field. source articles should returned before translated articles. like: article.findone(order: [ { type: [ 'source', 'translated' ] } ]); unfortunately there appears no built-in solution sorting enums. instead have sort by case , couldn't find documentation on how sequelize. what conventional approach here? sorting case hard in sequelize, sort field (the second answer in linked post) should possible: order: sequelize.fn('field', sequelize.col('type'), 'source', 'translated') it's supported mysql far know though
Read more

user interface - how to replace an ongoing process of image capture from another process call over the same ImageLabel in python's GUI TKinter -

i trying use following code create interactive gui changes color-space(hsv, rbg, grayscale etc) on event of button click. display opencv video in tkinter using multiprocessing being new python having problems multiprocessing , attempts on making gui change it's color space on button clicks hangs entire system. on it's implementation highly appreciated. thankyou. below code: import cv2 pil import image,imagetk import tkinter tk import numpy np multiprocessing import process , queue def quit_it(root,process): root.destroy() process.terminate() def black_andwhite(root,process): process.terminate p=process(target=capture_image, args=(5,queue, )) p.start() root.after(0, func=lambda: update_all(root, image_label, queue)) def update_image(image_label, queue): frame = queue.get() = image.fromarray(frame) b = imagetk.photoimage(image=a) image_label.configure(image=b) image_label._image_cache = b root.update() def update_all(root...
Read more