init | 易学教程

Can we ensure nullability of `+ (nonnull instancetype)sharedInstance;`?

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问题 This is a question on how to gracefully circumvent the nullability of init in NSObject class. So here is a classic objective-c implementation: + (instancetype)sharedInstance { static dispatch_once_t onceToken; static id sharedInstance; dispatch_once(&onceToken, ^ { sharedInstance = [[self alloc] init]; }); return sharedInstance; } But now I want to declare it as nonnull , if possible: + (nonnull instancetype)sharedInstance; Unfortunately, init returns a nullable instancetype value. Should I

Passing Linux boot opts to Init

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I would like to pass some parameters to a customized Linux init via the boot options configured in the bootloader at boot. I've written test init's in both Python and C. The Python version is able to see anything in the kernel boot options that doesn't have a '=' or '.' in it. The values are found in sys.argv. However, the C program doesn't seem to get passed the values. I would have thought the sys.argv list in Python was generated by parsing the **argv array. Below are the test scripts and screen shots that will hopefully help clarify. the kernel boot line is: kernel /grub/linux-2.6.38.4

InitWithNibName and viewDidLoad? [duplicate]

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This question already has answers here : Closed 7 years ago . Possible Duplicate: initWithNibName VS viewDidLoad I'm new at iOS development. I would just like to know the main differences between these 2 functions ? Thanks for your help viewDidLoad Is called when the view loads and is initiated/Unarchived and loaded into the memory. This is a great customisation stop. initWithNibName: Is used for initializing a certain class ( it is an overriden init method) with a xib file's name, the bundle parameter specifies the location of the file, you would pass nil for the main bundle, which is the

Purpose of init

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问题 I've done some reading and can't grasp this as fully as I'd like to. I'm making a little "choose your own adventure" game from the LPTHW tutorial, here's the full script: http://codepad.org/YWVUlHnU What I don't understand is the following: class Game(object): def __init__(self, start): self.quips = [ "You died. Please try again.", "You lost, better luck next time.", "Things didn't work out well. You'll need to start over." "You might need to improve your skills. Try again." ] self.start =

Swift Generic constraints in init

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问题 I have generic and I want to be able to initialize it with specific constrains. The constraints are only there for initialization. The rest of the class doesn't care. Here is a simplified example: struct Generic<T> { let compare: (T, T) -> Bool init<T: Equatable>(data: [T]) { let handler: (T, T) -> Bool = { $0 == $1 } compare = handler insert(data) } init(compareHandler: (T, T) -> Bool, data[T]) { compare = self.compareHandler insert(data) } } You can see there's two initializers. The second

Can I have two init functions in a python class?

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问题 I'm porting some geolocation java code from http://janmatuschek.de/LatitudeLongitudeBoundingCoordinates#Java (shown below) to python. It can be initialized using two functions (fromDegrees or fromRadians). I thought I could do something like class geoLocation: _radLat = 0 _radLong = 0 _degLat = 0 _degLong = 0 def fromDegrees(lat, long): #set _radLat, _radLong, _degLat, _degLong def fromRadians(lat, long): #set _radLat, _radLong, _degLat, _degLong ... But that does not seem optimal since I set

Swift Cannot assign to self in a method

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I've just faced a strange problem I have a class called Letter class Letter { init() {} } And I have an extension for this class: extension Letter { convenience init(file_path:String) { self = Letter.loadFromFile(file_path)} class func loadFromFile(file_path:String)->Letter {...} } I need to create and init with path to file and when i call Letter(file_path) I need a new object that returned by a func loadFromFile . How to assign in an init method or to return a new object? //Edit The same problem... Class functions that return instances of that class seems to be an anti-pattern in Swift. You

详解InitializingBean、initMethod和@PostConstruct

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转载： https://blog.csdn.net/nrsc272420199/article/details/95033223 1. InitializingBean、initMethod和@PostConstruct的作用实现了InitializingBean接口的类，可以在该类被注入到spring容器时达到某些属性先装配完成后，再去装配另一些属性的能力。而initMethod和@PostConstruct也可以达到相同的目的。注意：上文是一种用法，但思维不要局限。比如说我们的一个类里有一个属性，但是该属性不支持Spring注入，只能通过Build或者new的方式创建，而我们又想在spring装配Bean的时候一起将该属性注入进来，那使用InitializingBean、initMethod或@PostConstruct再合适不过了。 2. initMethod和InitializingBean 2.1 从initMethod说起进行过spring配置开发的肯定对下面的配置非常熟悉 <?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema

H2 “runscript” command turns all table names into uppercase

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问题 I have a sql script (it is just schema definition). The script is a modified version (getting rid of the bad characters h2 doesn't like) of a mysql dumb. The script runs and the schema is inserted into the h2 database, but the issue is that all of the database names are in uppercase ('xyz' gets converted to 'XYZ'). I need them to stay in lowercase because my application is looking for the lowercase (and all of the tables in the mysql db are lowercase). Why is this happening? How can I tell h2

Creating a pie chart in swift

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I'm trying to create a pie chart in swift, and would like to create the code from scratch rather than use a 3rd party extension. I like the idea of it being @IBDesignable, so I started with this: import Foundation import UIKit @IBDesignable class PieChart: UIView { var data: Dictionary<String,Int>? required init(coder aDecoder: NSCoder) { super.init(coder:aDecoder)! self.contentMode = .Redraw } override init(frame: CGRect) { super.init(frame: frame) self.backgroundColor = UIColor.clearColor() self.contentMode = .Redraw } override fun drawRect(rect: CGRect) { // draw the chart in here } } What