constraints

问题 Presently we do this... let parseDate defaultVal text = match DateTime.TryParse s with | true, d -> d | _ -> defaultVal Is it possible to do this... let d : DateTime = tryParse DateTime.MinValue "2015.05.01" 回答1: Yes. Welcome to the world of member constraints, ref, and byref values. let inline tryParseWithDefault defaultVal text : ^a when ^a : (static member TryParse : string * ^a byref -> bool) = let r = ref defaultVal if (^a : (static member TryParse: string * ^a byref -> bool) (text, &r

问题 Presently we do this... let parseDate defaultVal text = match DateTime.TryParse s with | true, d -> d | _ -> defaultVal Is it possible to do this... let d : DateTime = tryParse DateTime.MinValue "2015.05.01" 回答1: Yes. Welcome to the world of member constraints, ref, and byref values. let inline tryParseWithDefault defaultVal text : ^a when ^a : (static member TryParse : string * ^a byref -> bool) = let r = ref defaultVal if (^a : (static member TryParse: string * ^a byref -> bool) (text, &r

问题 I have UITabBarController based iPad app with containerView on the first tab. The containerView has standard vertical spacing to bottom layout guide. When I tap on the second tab and then go back to the first tab, my container moves down by 56 pts, the height of the tabBar and is then covered by the tabBar. I made 3 screenshots to illustrate that. The third screenshot shows hidden tabBar after the jump between tabs. It looks like the bottom layout guide went down to the edge. What is going on

问题 I have UITabBarController based iPad app with containerView on the first tab. The containerView has standard vertical spacing to bottom layout guide. When I tap on the second tab and then go back to the first tab, my container moves down by 56 pts, the height of the tabBar and is then covered by the tabBar. I made 3 screenshots to illustrate that. The third screenshot shows hidden tabBar after the jump between tabs. It looks like the bottom layout guide went down to the edge. What is going on

问题 I upgraded my Xcode today to 11 and just realised that Xcode doesn't allow me to create proportional height from a sub view to the view controller's root view anymore. I was able to do it till this morning with the previous Xcode version. The only workaround is to add another sub root view to the controller and move everything under it. This option will take too much time to re-design the setup the controller. Are you experiencing the same problem? This is from the new Xcode 11. As you can

问题 I am working in a project where database items are not deleted, but only marked as deleted. Something like this: id name deleted --- ------- -------- 1 Thingy1 0 2 Thingy2 0 3 Thingy3 0 I would like to be able to define something like a UNIQUE constraint on the name column. Seems easy, right? Let's imagine a scenario in which "Thingy3" is deleted, and a new one is created (perhaps years later). We get: id name deleted --- ------- -------- 1 Thingy1 0 2 Thingy2 0 3 Thingy3 1 ... 100 Thingy3 0

问题 Here's the code (I'm sorry if it's so long, but it was the first example I had); I'm using the CVaR example from CreditMetrics package by A. Wittmann and DEoptim solver to optimize: library(CreditMetrics) library(DEoptim) N <- 3 n <- 100000 r <- 0.003 ead <- rep(1/N,N) rc <- c("AAA", "AA", "A", "BBB", "BB", "B", "CCC", "D") lgd <- 0.99 rating <- c("BBB", "AA", "B") firmnames <- c("firm 1", "firm 2", "firm 3") alpha <- 0.99 # correlation matrix rho <- matrix(c( 1, 0.4, 0.6, 0.4, 1, 0.5, 0.6, 0

问题 I have a table defined by the following SQL: CREATE TABLE test ( id integer PRIMARY KEY NOT NULL UNIQUE, status text NOT NULL, enddate date, /* Checks */ CHECK (status IN ("Current", "Complete")) ); I'd like to add a constraint that requires enddate to be non-null if the status is "Complete". Is this possible? I am using SQLite v3.6.16. 回答1: How about: CHECK (status = "Current" or (status = "Complete" and enddate is not null)) 回答2: CREATE TABLE test ( id integer PRIMARY KEY, status text NOT

问题 In SQL Server, I have a new column on a table: ALTER TABLE t_tableName ADD newColumn NOT NULL This fails because I specify NOT NULL without specifying a default constraint. The table should not have a default constraint. To get around this, I could create the table with the default constraint and then remove it. However, there doesn't appear to be any way to specify that the default constraint should be named as part of this statement, so my only way to get rid of it is to have a stored

问题 I run the below code on a button press, however the bottom constraint does not seem to be obeyed. The subview (bandCardView) overflows the bottom of the parent view (formVw). How can I make these constraints obeyed? @objc private func cardBtnTouch(){ self.bandAccountView?.bankBtn.setSelected(selected: false) self.bandAccountView?.cardBtn.setSelected(selected: true) self.bandAccountView?.selectLbl.isHidden = true for subview in self.bandAccountView!.formVw.subviews{ subview.removeFromSuperview