optional-parameters

问题 Like Oracle, DB2 supports parameter defaults in stored procedures. Oracle syntax: CREATE OR REPLACE PROCEDURE p_default ( p_in_number IN number := 0, p_out_number OUT number, p_in_varchar IN varchar2 := '0', p_out_varchar OUT varchar2, p_in_date IN date := date '1981-07-10', p_out_date OUT date ) DB2 syntax: CREATE PROCEDURE p_default ( IN p_in_number INTEGER DEFAULT(0), OUT p_out_number INTEGER, IN p_in_varchar VARCHAR(10) DEFAULT('0'), OUT p_out_varchar VARCHAR(10), IN p_in_date DATE

问题 Scenario: I have a report that pulls up stats for agents for a certain date range (usually the same day, yesterday) which I've set as parameters. I've built the report in Visual Studio Report builder and the report works great. Challenge: Some agents are taken off calls and work on emails instead that day. So, though they are logged in, they can't be added to the call queue stats. Need: I need to add parameters which can select agents from the drop down (Ctrl+select) and have the report run

问题 You can declare optional parameters in an interface method but implementing classes are not required to declare the parameters as optional, as Eric Lippert explained. Conversely, you can declare a parameter as optional in an implementing class but not in the interface. So is there any reason to declare optional parameters in an interface? If not, why is it allowed? Examples: public interface IService1 { void MyMethod(string text, bool flag = false); } public class MyService1a : IService1 {

问题 I am trying to create this function below that takes one optional argument. It's an object, and the only prop needed is value however, I am looking to pass along any ...rest parameters that area also passed in. const useHook = <T extends { value: string }>({ value: v = '', ...props }: T = { value: '' } as T) => { const defaultValue = React.useMemo(() => v, [props]) const [value, setValue, resetValue] = Hooks.useState(defaultValue) const onChange = React.useCallback((e) => setValue(e.target

问题 I know that in Visual Basic, delegate function cannot contain optional parameters. But can a method take a delegate as an optional parameter? What I want to do is this: Delegate Sub MyDelegate(ByVal input As String) Sub MyDelegateDefault(ByVal input As String) 'by default do nothing' End Sub Sub MyDelegateCustom1(ByVal input As String) 'do something here' End Sub In a different part of code: Sub OtherFunction(ByVal str As String, Optional ByVal delegate As MyDelegate = AddressOf

问题 For example, if we have the following code, type Events = { SOME_EVENT: number OTHER_EVENT: string ANOTHER_EVENT: undefined } interface EventEmitter<EventTypes> { on<K extends keyof EventTypes>(s: K, listener: (v: EventTypes[K]) => void); } declare const emitter: EventEmitter<Events>; emitter.on('SOME_EVENT', (payload) => testNumber(payload)); emitter.on('OTHER_EVENT', (payload) => testString(payload)); function testNumber( value: number ) {} function testString( value: string ) {} which

问题 I have a general question as well as a specific use case. Optional parameters are easy enough: def func(a, b, c=None): ... and then anywhere c might be used in the body just write if c: first, or something along those lines. But what about when a certain combination of parameters is required? The general case is to consider any arbitrary situation of which exact parameters exist or not. For a function def func(a, b, c=None, d=None, e=None, f=None): ... this would include silly things like:

问题 So, after extensively searching, I found a lot of information about what the Missing.Value does passing the default value to an optional parameter. But somehow not a single mention about why is it more useful, than just leaving out the optional parameter alltogether in which case, it also gets it's default value. Came across it in a Ms Office interop code sample, but tried leaving it out, and works all the same, just as excpected, so, what gives? E.g. in : oWB = oXL.Workbooks.Add( Missing

问题 This question already has answers here : Option accepted with and without value (2 answers) Closed 6 years ago . I need to recognise if was given argument alone or with optional string or neither parser.add_argument(???) options = parser.parse_args() so ./prog.py --arg should store '' into options.arg, ./prog.py --arg=lol stores 'lol' into options.arg and ./prog.py left options.arg as None now I have: parser.add_argument("--arg", nargs="?",type=str,dest="arg") but when I run myprogram as .

问题 I have a function which takes optional parameters. However, these are not Option[?] but can be either set or null: private def div(id: String = null, cssClass: String = null): JQuery = { val optId = Option(id) val optCssClass = Option(cssClass) ... // deal with optId and optCssClass using the Scala-way™ ... } I am using "null", which I know should be avoided like the plague. However, it allows me to write code like this: div(id = "someId") // no cssClass div(id = "otherId", cssClass =