closures

问题 When I run the following Python3 code, def f(): x = 'foo' def g(): return x def h(y): nonlocal x x = y return g, h g, h = f() print(g()) h('bar') print(g()) I get foo bar I had believed that in Python, all local variables are essentially pointers. So in my mind, x was a pointer allocated on the stack when f() is called, so when f() exits, the variable x should die. Since the string 'foo' was allocated on the heap, when g() is called, I thought "ok, I guess g() kept a copy of the pointer to

问题 When I run the following Python3 code, def f(): x = 'foo' def g(): return x def h(y): nonlocal x x = y return g, h g, h = f() print(g()) h('bar') print(g()) I get foo bar I had believed that in Python, all local variables are essentially pointers. So in my mind, x was a pointer allocated on the stack when f() is called, so when f() exits, the variable x should die. Since the string 'foo' was allocated on the heap, when g() is called, I thought "ok, I guess g() kept a copy of the pointer to

问题 In chapter 13 of the Rust book, you implement a Cacher to use memoization to demonstrate functional programming and how to speed up long-running tasks. As an extra challenge, they recommend making the Cacher allow multiple keys using a HashMap and also leveraging generics to allow more flexibility. Try modifying Cacher to hold a hash map rather than a single value. The keys of the hash map will be the arg values that are passed in, and the values of the hash map will be the result of calling

问题 In chapter 13 of the Rust book, you implement a Cacher to use memoization to demonstrate functional programming and how to speed up long-running tasks. As an extra challenge, they recommend making the Cacher allow multiple keys using a HashMap and also leveraging generics to allow more flexibility. Try modifying Cacher to hold a hash map rather than a single value. The keys of the hash map will be the arg values that are passed in, and the values of the hash map will be the result of calling

问题 In chapter 13 of the Rust book, you implement a Cacher to use memoization to demonstrate functional programming and how to speed up long-running tasks. As an extra challenge, they recommend making the Cacher allow multiple keys using a HashMap and also leveraging generics to allow more flexibility. Try modifying Cacher to hold a hash map rather than a single value. The keys of the hash map will be the arg values that are passed in, and the values of the hash map will be the result of calling

问题 As it currently stands, this question is not a good fit for our Q&A format. We expect answers to be supported by facts, references, or expertise, but this question will likely solicit debate, arguments, polling, or extended discussion. If you feel that this question can be improved and possibly reopened, visit the help center for guidance. Closed 7 years ago . I have the name of a function in a variable, but everything is within a closure. With this variable I want to call the function,

问题 So I am using fabric plugin/Twitter-kit to use twitter api in my application. I want to get the image URL of profile picture of a celebrity. here is my code below. func getImageURL(celebrity :String) -> String{ var imageURL = "" let client = TWTRAPIClient() let statusesShowEndpoint = userSearch let params = ["q": celebrity, "page" : "1", "count" : "1" ] var clientError : NSError? let request = client.URLRequestWithMethod("GET", URL: statusesShowEndpoint, parameters: params, error:

问题 So I am using fabric plugin/Twitter-kit to use twitter api in my application. I want to get the image URL of profile picture of a celebrity. here is my code below. func getImageURL(celebrity :String) -> String{ var imageURL = "" let client = TWTRAPIClient() let statusesShowEndpoint = userSearch let params = ["q": celebrity, "page" : "1", "count" : "1" ] var clientError : NSError? let request = client.URLRequestWithMethod("GET", URL: statusesShowEndpoint, parameters: params, error:

问题 This question already has answers here : Returning data from async call in Swift function (11 answers) Closed 9 months ago . I'm trying to get current document count belongs to spesific user from Firebase. Whenever i try to assign count value to my variable in closure, value is always shown as nill. So that i did couple of research, as a result i figured out networking sometimes takes so long and it happens asynchronously. So if i'm not wrong due to asynchronous returning a value inside a

问题 I'm having trouble understanding closure syntax in Swift and Objective-C. Can someone tell me all possible ways in both languages to write a closure which accepts no arguments and returns nothing? 回答1: In Objective-C language void (^closureA)(void) = ^{ }; In Swift language let closureB: () -> () let closureC: () -> Void 回答2: Since you ask for all and since C is within Objective-C's reach and since you specify no parameters, this also gets the job done. void ( * f ) ( void ); // C function