default-value

How to set default value of TextBox empty string instead of null

由 女生的网名这么多〃 提交于 2019-11-27 02:32:37
问题 I may be out of date, but one principle I adhere to is avoid nulls as much as possible. However what I have found is that for a strongly typed view in which the user inputs the properties of an object I want to save, if some fields are not entered they are assigned as null. Then when you try to save the changes, the validation fails. So rather than set each property to an empty string, how can I automatically set each TextBox on a form to default to an empty string rather than a null? 回答1:

Is it possible to declare a public variable in vba and assign a default value?

由 ≯℡__Kan透↙ 提交于 2019-11-27 02:01:54
问题 I want to do this but it won't compile: Public MyVariable as Integer = 123 What's the best way of achieving this? 回答1: .NET has spoiled us :) Your declaration is not valid for VBA. Only constants can be given a value upon application load. You declare them like so: Public Const APOSTROPHE_KEYCODE = 222 Here's a sample declaration from one of my vba projects: If you're looking for something where you declare a public variable and then want to initialize its value, you need to create a Workbook

Difference between mutation, rebinding, copying value, and assignment operator

由 霸气de小男生 提交于 2019-11-27 01:57:47
问题 #!/usr/bin/env python3.2 def f1(a, l=[]): l.append(a) return(l) print(f1(1)) print(f1(1)) print(f1(1)) def f2(a, b=1): b = b + 1 return(a+b) print(f2(1)) print(f2(1)) print(f2(1)) In f1 the argument l has a default value assignment, and it is only evaluated once, so the three print output 1, 2, and 3. Why f2 doesn't do the similar? Conclusion: To make what I learned easier to navigate for future readers of this thread, I summarize as the following: I found this nice tutorial on the topic. I

Why do I have to assign a value to an int in C# when defaults to 0?

由 为君一笑 提交于 2019-11-27 01:52:39
问题 This works: class MyClass { int a; public MyClass() { int b = a; } } But this gives a compiler error ("Use of unassigned local variable 'a'"): class MyClass { public MyClass() { int a; int b = a; } } As far as I can tell this happens because in the first example, technically, the compiler doesn't know that 'a' is not assigned. In the latter example, 'a' is defined locally, and therefore is easy to track. But why does the latter example not work? Don't integers default to 0? Is this something

Is un-initialized integer always default to 0 in c?

由 …衆ロ難τιáo~ 提交于 2019-11-27 01:26:43
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? External and static variables are initialized to zero by default, this is guaranteed. Automatic and

How to set a default value in react-select

由 不问归期 提交于 2019-11-27 01:13:32
问题 i have an issue using react-select. I use redux form and i've made my react-select component compatible with redux form. Here is the code: const MySelect = props => ( <Select {...props} value={props.input.value} onChange={value => props.input.onChange(value)} onBlur={() => props.input.onBlur(props.input.value)} options={props.options} placeholder={props.placeholder} selectedValue={props.selectedValue} /> ); and here how i render it: <div className="select-box__container"> <Field id="side"

Setting Function Defaults R on a Project Specific Basis

由 牧云@^-^@ 提交于 2019-11-27 01:09:25
Commonly, I use the same function settings. I'm wondering if there is a method, other than having a new object in the path that is essentially a wrapper for the function, to set default arguments. For example: paste() has it's sep argument set to a space =" " , I'm tired of writing ,sep="" over and over. So is there a way to "temporarily" replace the function with my chosen defaults? paste(...,sep="") Can I accomplish this through packaging? I've sometimes noticed that, some packages force other equally named functions to be masked in the global environment. Ideally, I'd like something that

Getting a default value on index out of range in Python [duplicate]

由 风格不统一 提交于 2019-11-27 00:34:09
This question already has an answer here: How to get the nth element of a python list or a default if not available 8 answers a=['123','2',4] b=a[4] or 'sss' print b I want to get a default value when the list index is out of range (here: 'sss' ). How can I do this? In the Python spirit of "ask for forgiveness, not permission", here's one way: try: b = a[4] except IndexError: b = 'sss' In the non-Python spirit of "ask for permission, not forgiveness", here's another way: b = a[4] if len(a) > 4 else 'sss' 00500005 In the Python spirit of beautiful is better than ugly Code golf method, using

Default member values best practice

由 佐手、 提交于 2019-11-27 00:01:15
问题 Is it good practice when writing C++11 code to set default values for class members in the header file of the class? Or is it better to do this in the constructor of the class? EDIT: I mean: foo.h : #include <string> using std::string; class Foo{ private: string greet = "hello"; public: Foo(); }; VS foo.cpp (of course with the necessary header file, but without the in-class initialization): Foo::Foo(){ greet = "hello"; } Which one is better and why? 回答1: If a class member is always

std::map default value for build-in type

由 喜夏-厌秋 提交于 2019-11-26 22:32:05
Recently, I was confused by the std::map operator[] function. In the MSDN library, it says: "If the argument key value is not found, then it is inserted along with the default value of the data type." I tryed to search much more exactly explanation for this issue. For example here: std::map default value In this page, Michael Anderson said that "the default value is constructed by the default constructor(zero parameter constructor)". Now my quest comes to this:"what the default value for the build-in type?". Was it compiler related? Or is there a standard for this issue by the c++ stardard
订阅 default-value