instancetype | 易学教程

Confusion about initWithNavigationBarClass - how to use (new instanceType method)

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问题 This works great: UINavigationController *nc = [[UINavigationController alloc] initWithNavigationBarClass:[GTScrollNavigationBar class] toolbarClass:[UIToolbar class]]; nc.viewControllers = @[firstPage]; self.window.rootViewController = nc; but this does not work: UINavigationController *nc = [[UINavigationController alloc] initWithNavigationBarClass:[GTScrollNavigationBar class] toolbarClass:[UIToolbar class]]; self.window.rootViewController = nc; self.window.rootViewController

Confusion about initWithNavigationBarClass - how to use (new instanceType method)

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boto3 aws api - Listing available instance types

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问题 Instance types: (t2.micro, t2.small, c4.large...) those listed here: http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/instance-types.html I want to access a list of these through boto3. something like: conn.get_all_instance_types() or even conn.describe_instance_types()['InstanceTypes'][0]['Name'] which everything seems to look like in this weird api. I've looked through the docs for client and ServiceResource, but i can't find anything that seems to come close. I haven't even found a hacky

Is it okay to return a subclass from a class constructor that uses instancetype?

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问题 I have a class method in a category to construct a Cocoa collection in some way that the built-in initializers don't allow. Due to the limited initializer functionality, I have to use the mutable version of the collection to actually build it. Here's an example for NS{Mutable}IndexSet : @implementation NSIndexSet (WSSNonContiguous) + (instancetype)WSSIndexSetFromMask:(NSUInteger)mask { NSMutableIndexSet * set = [NSMutableIndexSet indexSet]; for( NSUInteger i = 0; i < (sizeof(NSUInteger) * 8);

Why does initWithCoder not return instancetype?

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问题 It seems that most init methods in Objective-C now tend to return instancetype instead of id . See [UIView initWithFrame:], [UIViewController initWithNibName:bundle:], [NSArray init] and siblings, etc. But initWithCoder uses id . Why is this? Has it just not been updated yet? Or is there a reason it has to be id ? 回答1: It is not updated yet. You can still code it with instance type. - (instancetype)initWithCoder:(NSCoder *)aDecoder { self = [super initWithCoder:aDecoder]; if (self) { //... }

instancetype vs class name for singleton?

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问题 From what I understand, instancetype declares to the compiler that the return type of the method is the same as the class receiving the message. Traditionally I've always declared my singleton initializers with the class name explicitly set as the return type: @interface MyClass : NSObject + (MyClass *)sharedInstance; @end Now I'm wondering if I should use instancetype instead, like so: @interface MyClass : NSObject + (instancetype)sharedInstance; @end In the end the result is the same, I'm

Confusion about initWithNavigationBarClass - how to use (new instanceType method)

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This works great: UINavigationController *nc = [[UINavigationController alloc] initWithNavigationBarClass:[GTScrollNavigationBar class] toolbarClass:[UIToolbar class]]; nc.viewControllers = @[firstPage]; self.window.rootViewController = nc; but this does not work: UINavigationController *nc = [[UINavigationController alloc] initWithNavigationBarClass:[GTScrollNavigationBar class] toolbarClass:[UIToolbar class]]; self.window.rootViewController = nc; self.window.rootViewController.viewControllers = @[firstPage]; // ERROR how can it be? Thanks self.window.rootViewController.viewControllers = @

boto3 aws api - Listing available instance types

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Instance types: (t2.micro, t2.small, c4.large...) those listed here: http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/instance-types.html I want to access a list of these through boto3. something like: conn.get_all_instance_types() or even conn.describe_instance_types()['InstanceTypes'][0]['Name'] which everything seems to look like in this weird api. I've looked through the docs for client and ServiceResource, but i can't find anything that seems to come close. I haven't even found a hacky solution that lists something else that happen to represent all the instance types. Anyone with more

Why is instancetype used?

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Can someone please explain to me (in simple terms) why an instancetype is used in Objective-C? - (instancetype) init { self = [super init]; if (self) { // Custom initialization } return self; } It's to increase type safety. Back in the old days, initialisers just returned an object of type id (any object). With normal initialisers (those that begin with "init", "alloc" or "new"), this wasn't usually a problem. The compiler would automatically infer the type that it returned and therefore restrict any method calls on the object to the instance methods of that class. However, this was a problem

Why is instancetype used?

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问题 Can someone please explain to me (in simple terms) why an instancetype is used in Objective-C? - (instancetype) init { self = [super init]; if (self) { // Custom initialization } return self; } 回答1: It's to increase type safety. Back in the old days, initialisers just returned an object of type id (any object). With normal initialisers (those that begin with "init", "alloc" or "new"), this wasn't usually a problem. The compiler would automatically infer the type that it returned and therefore