callback | 易学教程

unable to receive callback from second view controller

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问题 I have got two view controllers. Im trying to pass data to the previous viewcontroller I have the following code in my second view controller CEPeoplePickerNavigationController @class CEPeoplePickerNavigationController; @protocol CEPeoplePickerNavigationControllerDelegate <NSObject> - (void)previousViewController:(CEPeoplePickerNavigationController *)controller itemToSend:(NSString *)item; @end @interface CEPeoplePickerNavigationController : UIViewController <UITableViewDelegate

How can I use the same callback function to trace multiple variables?

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问题 I would like to display the value of several StringVar() with some formatting on Labels. import tkinter as tk keys = range(2) # 2 for simplicity root = tk.Tk() myVars = {key: tk.StringVar() for key in range(5)} myStrVars = {key: tk.StringVar() for key in range(5)} def callback0(*args): blah = '{0:.3f}'.format(float(myVars[0].get())) myStrVars[0].set(blah) def callback1(*args): blah = '{0:.3f}'.format(float(myVars[1].get())) myStrVars[1].set(blah) #etc... myCallbacks = {0: callback0, 1:

How to code and wrap with ctypes a python function needed as callback by sqlite3?

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问题 I'm trying to perform sqlite3_exec from python to extract line by line the contents of a database. According to the C API, I need a Callback function which will perform the iteration. I have coded the following with a lot of help from internet: UPDATED with @eryksun pièces of advice import ctypes def extractor(unused, num_columns, pcolumn, pcolumn_name): for column in range(0,num_columns): if pcolumn[i] != None: print pcolumn[i] sqlite3DLL = ctypes.CDLL("C:\\Python\\PYTHON\\DLLs\\sqlite3.dll"

Scoping problem with Javascript callback

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问题 I am having some trouble getting a callback function to work. Here is my code: SomeObject.prototype.refreshData = function() { var read_obj = new SomeAjaxCall("read_some_data", { }, this.readSuccess, this.readFail); } SomeObject.prototype.readSuccess = function(response) { this.data = response; this.someList = []; for (var i = 0; i < this.data.length; i++) { var systemData = this.data[i]; var system = new SomeSystem(systemData); this.someList.push(system); } this.refreshList(); } Basically

How does Javascript match the parameters in the callback function?

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问题 I just started to learn Javascript, and callback functions seem hard to understand. One question I have is how javascript matches the parameters in a callback function? for example in the following forEach loop: var friends = ['Mike', 'Stacy', 'Andy', 'Rick']; friends.forEach(function(eachName, index){ console.log(index + 1 + ". " + eachName); }); Is it by default that the forEach function will pass index to the second parameter and entry to the first parameter in the callback function? In

Callback function not callable

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问题 I've read in python documentation that it is possible to call a function from command line, so I've used optparse module to return a huge text from a function but my code doesn't work! I think I've done everything right. def HelpDoc(): return """ SOME HUGE TEXT """ parser = OptionParser(usage="%prog ConfigFile") parser.add_option("-g", "--guide", action = "callback", callback=HelpDoc(), help = "Show help documentation") (options,args) = parser.parse_args() Traceback parser.add_option("-g", "-

初步学习jquery学习笔记（二）

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jQuery事件 jquery是为事件处理而设计的什么是事件? 页面对不同访问者的相应叫做事件。事件处理程序指的是html中发生某些事件所调用的方法实例: 在元素上移动鼠标选取单选按钮点击元素触发:产生事件的过程，比如点击按钮常见的dom事件鼠标事件键盘事件表单事件文档/窗口事件 click keypress submit load dblclick keydown change resize mouseenter keyup focus scroll mouseleave blur unload hover jQuery中事件以及语法在jquery中，大多数dom事件都有一个等效的方法页面中指定一个点击事件 $("p").click();//指定一个点击事件 //定义触发后的事件 $("p").click( function(){ //动作触发后执行的代码 } ) 常见jQuery中事件以及方法 $(document).ready() $(doucument).ready()方法允许我们在文档完全加载后执行函数) click() click()方法是当按钮点击事件被触发会调用的一个函数，该函数在用户点击html元素的时候执行 $("p").click(function(){ $(this).hide(); }) dbclick() 当双击元素时候

Javascript function for handling multiple unknown callbacks

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问题 I have a scenario where I would like to send in 2 or more functions (as parameters) into a handler function, and have that handler function execute each passed function as a callback function for the preceding function. Here is a general concept of the function I am trying to write: function functionChain() { // MAKE SURE WE HAVE AT LEAST 1 PARAMETER if ( arguments.length < 1 ) { return; } // for each parameter, call it (as a function) for ( var i=0; i<arguments.length; i++) { if ( typeof

__invoke() on callable Array or String

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问题 How would one write PHP code to call all "Callables" with __invoke() ? The desire here is pass by reference, which is deprecated with call_user_func[_array]() . I did see that there is a package out there, TRex\Reflection\CallableReflection , but this seems to utilize call_user_func() in the background, and would suffer the same issue. <?php function passthrough_invoke(callable $callback) { return $callback->__invoke(); } function passthrough_user(callable $callback) { return call_user_func(

How to properly check and log http status code using promises and node.js?

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问题 I am new to JavaScript and very new to node.js framework, just started using it a few days ago. My apologies if my code is nonsensical, the whole idea of promises and callbacks is still sinking in. That being said my question is the following I am trying to figure out if certain request to websites are successful or cause an error based on the range of their status code response. I am working with an array of websites and what I've done so far is below, I do however get a TypeError: Cannot