switch-statement

问题 I have a reactive form in which I validate the different fields with ngif. For example: <mat-form-field> <input matInput formControlName="name" placeholder="Name"> <mat-error *ngIf="personForm.get('name').hasError('required')">Name is empty</materror> <mat-error *ngIf="personForm.get('name').hasError('minlength')">Needs more than 3 characters</mat-error> </mat-form-field> Would it be possible to do the same thing in a switch case statement and how would one go on about doing this? I imagened

问题 I have a function that pops-up a message box after you click on a button using PyQt4 in python. I use 'sender()' to determine which button was clicked and then set the text of pop-up window accordingly. This function works perfectly with 'if statements'. However I was wondering how do I write a function with same functionality using a dictionary (since there is no switch statement in python and there are too many if statements in my code)? def pop_up(self): msg = QtGui.QMessageBox() msg

问题 I'm working on a function for calculations of a single numeric variable (double). It should takes it's components from another data frame that stores different equations which are broken up into their single pieces (I use linear regression equations here so it's about the two variables/columns slope and intercept). Depending on one condition (a name/specific string) which is stored in the equations table as well the function should use the slope and intercept from the same row. The actual

问题 I am trying to implement my own programing language in C++. When an error occours in my language (for example, during lexical analysis), an exception is thrown to be catched by the main function which then prints its message. The exception can be of different types: either SyntaxError , or FunctionError and so on, all based on the Error class so that they can all be catched even being of different types. Each sub class of errors anyway can generate different types of error, each one requiring

问题 I tried to design a program which counts the vowels in a sentence. In my code, I used a foreach statement with the if/else if statement. I would like to convert these line of code using the switch statement but I'm not really sure where to go. Do I need to add a new method? I would appreciate your help. This is what I tried so far: I checked this one is very wrong. The case 1 for example needs to have a constant. I'm not sure what constant shall I use here. foreach (char v in yourSentence) {

问题 I use NSUserDefaults to save a switch on/off and so far it is good. It remembers the switch position in next session. Now to the thing which I do not understand. I use the same switch (with the same name)in another view, let´s say a flip view which is pushed in from the first view. If I change the switch in the first view it is automatically changed in the flip view. But the other way round, if I change it in the flip view it is not changed in the first view when I go back. Only if I restart

问题 I'd like this code to work. I have an enum where the case Direction.Right takes a distance parameter. enum Direction { case Up case Down case Left case Right(distance: Int) } Now another enum that can take a Direction parameter. enum Blah { case Move(direction: Direction) } let blah = Blah.Move(direction: Direction.Right(distance: 10)) When I switch on the Blah enum I want to be able to conditionally switch on the Move.Right like this... switch blah { case .Move(let direction) where direction

问题 I am trying to make a switch statement that takes in a word into an array and then throws each letter through a switch statement and allocates a point to each letter depending on which letter it is and giving a final point value for the word, and I can't seem to get the array part right. Any help would be appreciated! int main(){ int letter_points = 0; char word[7]; int word_length = 7; int i; printf("Enter a Word\n"); scanf("%s", word); for(i = 0; i < word_length; i++){ switch(word){ //1

问题 I am trying to find a way to evaluate a switch - case statement using a member variable in the case part. I thought that having a global static variable like below would be allowed as const-expression. Unfortunately the compiler tells me the opposite: error: ‘ll’ cannot appear in a constant-expression error: ‘.’ cannot appear in a constant-expression Is there any keyword or anything that would allow this idea to work? I am not an expert of C++11, and I heard about constexpr . enum MyEnum2 {A

问题 Some context: I'm parsing an accounting ledger which has account1 and account2 as int types. Each is a number in the range [0, 99999]. I have many combinations to consider. Ideally I'd like to use something like switch (account1, account2){ case (1,1): /*account1 is 1, account2 is 1*/ case (2,1): /*account1 is 2, account2 is 1*/ } and so on. (I only need to consider about 20 possible combinations). Is there a way I can achieve this in Java? I've considered this question Storing number pairs