scope

问题 MyAppDelegate *appD; appD = [UIApplication sharedApplication]; if(appD.sw1.on) NSLog(@"It is ON"); else NSLog(@"It is OFF"); Gives no error while compiling. Runs without any warning, but it doesn't work. I dont see what the problem is. ... EDIT: OMG, should have called delegate method too: appD = (MyAppDelegate *)[[UIApplication sharedApplication] delegate]; 回答1: I recommend you this method to share the app delegate: https://coderwall.com/p/z4h4uw?i=2&p=1&q=&t%5B%5D=%21%21mine&t%5B%5D=%21

问题 Suppose I defined a function in file function.c, and in main.c I create multiple pthreads to execute the function in function.c. If in function.c, I define a global variable, for example, int foo; Then, my question is, does every thread has its own instance of this variable "foo" or do they share a single "foo"? 回答1: They share a single foo variable. Global variable always exists only once per process and is usually protected by mutex to avoid concurrent access. Since C11 you can use thread

问题 I have a type that looks a little something like this: var x = function(){ this.y = function(){ } this.z = function(){ ... this.A = function(){ CALLING POINT } } } From calling point, I'm attempting to call function this.y. I don't need to pass any parameters, but when I set some stuff from this.A, I need to call this.y. Is this possible? I'm OK with passing extra parameters to functions to make it possible. 回答1: Is this possible? Yes, you can assign this reference to another variable and

问题 I have see the following code... The first call of (next-num) returns 1 , and the second returns 2 . (define next-num (let ((num 0)) (lambda () (set! num (+ num 1)) num))) (next-num) ; 1 (next-num) ; 2 What I can not understand is... num is created by let inside next-num , it is kind of a local variable... How does scheme know that each time next-num is called, the value of num is not erased by let ((num 0)) ; How does scheme know that it is always the same num that we modify whenever next

问题 This question already has answers here : Accessing class variables from a list comprehension in the class definition (5 answers) Closed 2 years ago . Here I'm not able to access the class variable inside a Python's list comprehension . class Student: max_year = 18 year_choice = [i for i in range(100) if i > max_year] def __init__(self, name): self.name = name print (self.year_choice) Student('Blah') But it's working fine in Python 2. ../workspace$ python student.py [19, 20, 21, 22, 2.... 99]

问题 This is a bit of a follow-up to this question. Why is locality determined at compile time and not at execution time? Is it purely for performance? Are there languages that look up their variables at execution time? I.e. every time a variable is accessed, this variable is first searched in the local scope and then the search escalates through all enclosing scopes? How do ECMA languages handle this? To put question 2 in other words: Are there languages where the following code (in the necessary

问题 This is a bit of a follow-up to this question. Why is locality determined at compile time and not at execution time? Is it purely for performance? Are there languages that look up their variables at execution time? I.e. every time a variable is accessed, this variable is first searched in the local scope and then the search escalates through all enclosing scopes? How do ECMA languages handle this? To put question 2 in other words: Are there languages where the following code (in the necessary

问题 This question already has answers here : JavaScript closure inside loops – simple practical example (44 answers) Closed 3 years ago . Question How can a callback function retain a local variable from whence it was created? Simple example I'm creating a video player. It will have sliders to control the saturation, contrast, and hue. When the user plays with the sliders, it needs to acknowledge which slider got changed and what value it got changed to. The problem is that the name of the slider

问题 Can someone explains the scope binding of the following code please window.name = "window"; object = { name: "object", method: function() { nestedMethod: function() { console.log(this.name); } nestedMethod(); } } object.method(); // print 'window' I think my question is more about this ...why is this losing the scope and default to the global scope ? do all the anonymous functions that we created will go on the global scope ? 回答1: Whenever you call a function, simply by writing func() , this

问题 I have the following function: f1<-function(x){ iih_data<-...stuff... ...more stuff... cl <- makeCluster(mc <- getOption("cl.cores", 6)) clusterExport(cl, c("iih_data")) clusterEvalQ(cl, require(lme4)) Tstar<-parCapply(cl, ystar, function(x){ ostar=glmer(x ~ GENO + RACE + (1|GROUP), family="binomial",data=iih_data,nAGQ=1) fixef(ostar)[2]/sqrt(vcov(ostar)[2,2]) }) stopCluster(cl) ...more stuff... } But I get this error: Error in get(name, envir = envir) : object 'iih_data' not found I am