callback | 易学教程

Activerecord callback, previous_changes vs. changes

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问题 I'm trying to understand what the difference between these two methods is. Here is the documentation for each: https://apidock.com/rails/v4.2.7/ActiveModel/Dirty/previous_changes https://apidock.com/rails/v4.2.7/ActiveModel/Dirty/changes It appears to me after reading this documentation that previous_changes is what was changed after the changes are done, meaning in an after_* filter, while changes is what will be changed, meaning it's useful in a before_* filter. Am I misunderstanding this?

How to redirect back to my iOS app after logging in on FitBit login page?

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问题 I am developing a very basic iOS app with Swift. Just to read the heart rate data. I am using SFSafariViewController. As known, I first need to register my app on dev.fitbit.com. The registration form requires a callback URL to be entered. After logging in successfully, FitBit always redirects me back to that entered callback URL. What should I do/code/configure to be able to redirect user back to my iOS app after logging in successfully? 回答1: What you need to do is to add the application(_

Node.js其他模块

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清明假期过得挺快，3天说没就没了，天热了今天把房间打扫了一下，看着挺舒心的。周六了解了下进程管理的Process模块，由于进程管理知识也比较多，今天先把其他的一些模块了解一下，进程管理这块以后慢慢学。一、OS模块 OS模块主要是获取操作系统信息。 var os = require('os'); //返回一个指向操作系统默认临时目录的字符串如果需要临时存储文件，然后再删除可以放在这 console.log("tmpdir :\t" + os.tmpdir()); //根据机器的体系结构，对于大端和小端编码，分别返回BE或LE console.log("endianness :\t" + os.endianness()); //机器的主机名 console.log("hostname :\t" + os.hostname()); //操作系统类型字符串类型 console.log("type :\t\t" + os.type()); //平台名称字符串类型 console.log("platform :\t" + os.platform()); //体系结构字符串类型 console.log("arch :\t\t" + os.arch()); //操作系统发布版本 console.log("release :\t" + os.release()); //操作系统已经运行多久

Sails.js Can't set headers after they are sent

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问题 I am using sailsjs v0.10.5. I am trying to redirect to login after verifying user email and update the database before redirect. I am using redirection in my update callback. But it sending the error after updating the database 'Cant send headers after they are sent'. The following is the code am using for redirection: verifyEmail: function(req, res){ var userId = req.param('userId'); User.update({id: userId},{isVerified: true}).exec(function(err, user) { if (!err) { req.flash('error', 'Your

Understanding Higher Order functions in Javascript

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问题 I am currently reading Eloquent Javascript Chapter 5. They give the following example which is confusing the hell out of me. function greaterThan(n) { return function(m) { return m > n; }; } var greaterThan10 = greaterThan(10); console.log(greaterThan10(11)); // → true Can anyone break this down to me as simply as possible. I have huge trouble with callbacks. Especially when it comes to situations like these. 回答1: Higher-Order functions basically mean two things: Functions can take other

How do I avoid callback hell on swift functions that I didn't write?

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问题 I don't want this to be misconstrued as a duplicate. I want to deal with callback hell arising from API calls from Firestore (database by Firebase, a Google platform). I can't modify their function declarations, so I assume I will have to wrap their functions with some of my code. For example, in the code below, the function eventCreatedSuccessfully() can only be called after the asynchronous function completes. eventCreatedSuccessfully() also contains a function call to firebase that has a

asp.net mvc equivalent of rails callback before_save

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问题 Hi i'm looking for a asp.net mvc callback for elaborate data before save a model. In rails there is before_save. Thanks 回答1: If you are using Entity Framework (which your tag indicates), then this StackOverflow post should be able to help you out. Basically you can intercept the SavingChanges event, and do whatever you want. Put this in a partial class that adds the following methods to your object context: partial void OnContextCreated() { SavingChanges += DoWhatYouMust; } private void

stop a curl transfer in the middle

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问题 i could only think of curl_close() from one of the callback functions. but php throws a warning: PHP Warning: curl_close(): Attempt to close cURL handle from a callback. any ideas how to do that? 回答1: you can return false or something what is not length of currently downloaded data from callback function to abort curl 回答2: If the problem is that is taking too long to execute the curl, you could set a time, example <?php $c = curl_init('http://slow.example.com/'); curl_setopt($c, CURLOPT

Android callback listener - send value from pojo in SDK to an application's activity

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问题 I have a java class buried deep in an SDK that performs an action and returns a boolean. It has no knowledge of the application's main activity , but I need the main activity to receive that boolean value. I've seen a lot of questions regarding callbacks, broadcasts, and listeners but they all seem to have knowledge of the activity. My pojo does have an activityContext but I don't know how to get the value back to the application's main activity. I'm already using an AsyncTask in my pojo and

Alterantive for callbacks using std::function

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问题 Currently I am trying out a code that does essentially the following: void f(int x) { cout << "f("<<x<<")" << endl; } class C { public: void m(int x) { cout << "C::m("<<x<<")" << endl; } }; class C2 { public: void registerCallback(function<void(int)> f) { v.push_back(f); } private: vector<function<void(int)>> v; void callThem() { for (int i=0; i<v.size(); i++) { v[i](i); } } }; int main() { C2 registrar; C c; registrar.registerCallback(&f); // Static function registrar.registerCallback(bind(