flags | 易学教程

How to run code inside a loop only once without external flag?

阅读更多关于 How to run code inside a loop only once without external flag?

问题 I want to check a condition inside a loop and execute a block of code when it's first met. After that, the loop might repeat but the block should be ignored. Is there a pattern for that? Of course it's easy to declare a flag outside of the loop. But I I'm interested in an approach that completely lives inside the loop. This example is not what I want. Is there a way to get rid of the definition outside of the loop? bool flag = true; for (;;) { if (someCondition() && flag) { // code that runs

Activity.finishAffinity() vs Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK

阅读更多关于 Activity.finishAffinity() vs Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK

In Android, if you want to clear your current Activity stack and launch a new Activity (for example, logging out of the app and launching a log in Activity ), there appears to be two approaches. Are there any advantages to one over the other if your target API level is above 16? 1) Finish Affinity Calling finishAffinity() from an Activity. Activity.finishAffinity 2) Intent Flags Intent intent = new Intent(this, LoginActivity.class); intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK); startActivity(intent); finish(); The finishAffinity() approach is suitable for >=

How to use flags enums in Linq to Entities queries?

阅读更多关于 How to use flags enums in Linq to Entities queries?

I have a [Flags] enum like this: [Flags] public enum Status { None = 0, Active = 1, Inactive = 2, Unknown = 4 } A Status enum may contain two values such as: Status s = Status.Active | Status.Unknown; Now I need to create a linq query (LINQ to ADO.NET Entities) and ask for records whose status is s above, that is Active or Unknown; var result = from r in db.Records select r where (r.Status & (byte)s) == r.Status Of course I get an error, because LINQ to Entities only knows to handle primitive types in the Where clause. The error is: Unable to create a constant value of type 'Closure type'.

PowerShell mandatory parameter depends on another parameter

阅读更多关于 PowerShell mandatory parameter depends on another parameter

问题 I have a PowerShell function which changes the registry key values. Code: param( [Parameter()] [switch]$CreateNewChild, [Parameter(Mandatory=$true)] [string]$PropertyType ) It has a parameter, "CreateNewChild", and if that flag is set, the function will create the key property, even if it wasn't found. The parameter "PropertyType" must be mandatory, but only if "CreateNewChild" flag has been set. The question is, how do I make a parameter mandatory, but only if another parameter has been

Changing the RegExp flags

阅读更多关于 Changing the RegExp flags

问题 So basically I wrote myself this function so as to be able to count the number of occurances of a Substring in a String: String.prototype.numberOf = function(needle) { var num = 0, lastIndex = 0; if(typeof needle === "string" || needle instanceof String) { while((lastIndex = this.indexOf(needle, lastIndex) + 1) > 0) {num++;} return num; } else if(needle instanceof RegExp) { // needle.global = true; return this.match(needle).length; } return 0; }; The method itself performs rather well and

Autotools : how to set global compilation flag

阅读更多关于 Autotools : how to set global compilation flag

I have a project with several sources directories : src/A /B /C In each, the Makefile.am contains AM_CXXFLAGS = -fPIC -Wall -Wextra How can avoid repeating this in each source folder ? I tried to modifiy src/Makefile.am and the configure.in, but without success. I thought I could use AC_PROG_CXX to set the compilation flags globally but can't find much documentation on how to use those macro (do you have any pointer to such a documentation ?). Thanks in advance adl You can do several things: (1) One solution is to include a common makefile fragment on all your Makefile.am s: include $(top

Flags with web services

阅读更多关于 Flags with web services

问题 I have a flag attribute enumeration that is behind a web service as follows: [Serializable,Flags] public enum AccessLevels { None = 0, Read = 1, Write = 2, Full = Read | Write } My problem is the consumer of my web service does not have the original constant values of the enum. The resulting proxy class client side has something that amounts to this: { None = 1, Read = 2, Write = 4, Full = 8 } And thus when the consumer is checking for "Read" access this will be false even when "testItem" is

What does regex' flag 'y' do?

阅读更多关于 What does regex' flag 'y' do?

MDN says: To perform a "sticky" search, that matches starting at the current position in the target string, use the y flag. I don't quite understand it. Regular expression objects have a lastIndex property, which is used in different ways depending on the g (global) and y (sticky) flags. The y (sticky) flag tells the regular expression to look for a match at lastIndex and only at lastIndex (not earlier or later in the string). Examples are worth 1024 words: var str = "a0bc1"; // Indexes: 01234 var rexWithout = /\d/; var rexWith = /\d/y; // Without: rexWithout.lastIndex = 2; // (This is a no-op

How to run code inside a loop only once without external flag?

阅读更多关于 How to run code inside a loop only once without external flag?

I want to check a condition inside a loop and execute a block of code when it's first met. After that, the loop might repeat but the block should be ignored. Is there a pattern for that? Of course it's easy to declare a flag outside of the loop. But I I'm interested in an approach that completely lives inside the loop. This example is not what I want. Is there a way to get rid of the definition outside of the loop? bool flag = true; for (;;) { if (someCondition() && flag) { // code that runs only once flag = false; } // code that runs every time } It's fairly hacky, but as you said it's the