default-value

问题 I am well aware that if you have a class method that uses the enum's class name for type hinting, there is a hack to get it to work for Python 3.6 and below. Instead of... class Release(Enum): ... @classmethod def get(cls, release: Release): ... You need to use the string value like so... class Release(Enum): ... @classmethod def get(cls, release: "Release"): ... I believe in Python 3.7 and above there is a pythonic way around this "hack" where you don't have to use quotes. The reason is

问题 I am well aware that if you have a class method that uses the enum's class name for type hinting, there is a hack to get it to work for Python 3.6 and below. Instead of... class Release(Enum): ... @classmethod def get(cls, release: Release): ... You need to use the string value like so... class Release(Enum): ... @classmethod def get(cls, release: "Release"): ... I believe in Python 3.7 and above there is a pythonic way around this "hack" where you don't have to use quotes. The reason is

问题 I am well aware that if you have a class method that uses the enum's class name for type hinting, there is a hack to get it to work for Python 3.6 and below. Instead of... class Release(Enum): ... @classmethod def get(cls, release: Release): ... You need to use the string value like so... class Release(Enum): ... @classmethod def get(cls, release: "Release"): ... I believe in Python 3.7 and above there is a pythonic way around this "hack" where you don't have to use quotes. The reason is

问题 In a C++ function with multiple arguments, I would like one of the arguments to have a default value which is itself a function of the other arguments. For example, int f1( int m ); int f2( int n1, int n2 = f1( n1 ) ) { // Do stuff with n1 and n2 } This won't compile, but hopefully it makes clear the behavior I want for the function f2. Its caller should be able to manually pass it a value for n2, but by default the value of n2 should be determined by calling f1 on n1. What are some

问题 I'm reading source code of nginx and find it's not initializing many of the numerical variables, including ngx_int_t ngx_last_process; ,here ngx_int_t defined as long int #if 0 ngx_last_process = 0; #endif So here @Igor Sysoev think it unnecessary to do the initialization? But in the programe it's assuming the default value is 0 : for (s = 0; s < ngx_last_process; s++) { if (ngx_processes[s].pid == -1) { break; } } Is it guranteed that un-initialized variable will have 0 value in c at all?

问题 I have a Form that contains some fields, one of them is a date field: GestureDetector( onTap: () { selectDate(context); }, child: AbsorbPointer( child: TextFormField( initialValue: dataEvento, decoration: InputDecoration( labelText: 'Date ${dataEvento}', labelStyle: TextStyle( fontFamily: 'acumin-pro', fontSize: MediaQuery.of(context).size.height * 0.022, fontWeight: FontWeight.bold, color: Colors.grey), focusedBorder: UnderlineInputBorder( borderSide: BorderSide(color: dataUserGlobal.yellow)

问题 I have a column rndm in my table [guests]. Now, for the field Default value or Binding for the table, whenever a new row is inserted I want to automatically insert a 10-character random string into this column as the default value. This random string may not contain special characters, only characters from a-zA-Z0-9 . What is the best approach to achieve this? To be clear: I don't want to generate this random string in my .NET code, I want it to be generated within SQL Server. And I want to

问题 The following code is not valid in C++ struct Test { int x; int y; }; void function(Test A, int n = A.x) { ... } because the default parameter A.x depends upon A. Is there a way to go around this limitation? The reason why I want to do this is the following. I have a class Vector that behaves very closely to std::vector but has a member allocator_ which is responsible for allocating memory. My copy constructor takes 2 parameters: Vector(const Vector& A, Allocator& allocator) { ... } Such copy

问题 At times I have a variable that I want to default to something and if something else is set change it to something else. The question is. What is preferred? Setting the default value and then changing it if the condition is met or setting the condition only once depending on the initial check with an added else? Example in code. if x: y = '%s-other' % x else: y = 'some_default' The other option would be. y = 'some_default' if x: y = '%s-other' % x This isn't always an argument passed in to a

问题 I am aware this is bad form and that default-values should be specified in the declaration, but if you would please indulge me for a moment.. why does this compile? and what is happening exactly? #include <iostream> using namespace std; class test { public: test(int n); }; test::test(int n = 666) { cout << n; } int main() { test t; cin.sync(); cin.ignore(); return 0; } Output: 666 .. how do templates affect the same piece of code? template <class T> class test { public: test(int n); };