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How to implement a rule engine?
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This snippet compiles the Rules into fast executable code (using Expression trees) and does not need any complicated switch statements:
(Edit : full working example with generic method)
public Func<User, bool> CompileRule(Rule r)
{
var paramUser = Expression.Parameter(typeof(User));
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Loading and parsing a JSON file with multiple JSON objects
...t is not a valid JSON value as there is no top-level list or object definition.
Note that because the file contains JSON per line, you are saved the headaches of trying to parse it all in one go or to figure out a streaming JSON parser. You can now opt to process each line separately before moving ...
How to dismiss ViewController in Swift?
...s a ViewController in swift by calling dismissViewController in an IBAction
20 Answers
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What's the difference between QMainWindow, QWidget and QDialog?
... to be shown as a window. It will always appear in a window, and has functions to make it work well with common buttons on dialogs (accept, reject, etc.).
QMainWindow is designed around common needs for a main window to have. It has predefined places for a menu bar, a status bar, a toolbar, and o...
Print string to text file
...on2.7 and higher you can use {} instead of {0}
In Python3, there is an optional file parameter to the print function
with open("Output.txt", "w") as text_file:
print("Purchase Amount: {}".format(TotalAmount), file=text_file)
Python3.6 introduced f-strings for another alternative
with open("...
How do I remove a MySQL database?
You may notice from my last question that a problem caused some more problems, Reading MySQL manuals in MySQL monitor?
6 A...
Check whether or not the current thread is the main thread
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Have a look at the NSThread API documentation.
There are methods like
- (BOOL)isMainThread
+ (BOOL)isMainThread
and + (NSThread *)mainThread
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Save string to the NSUserDefaults?
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As of iOS 12, calling synchronize is no longer needed: stackoverflow.com/a/57218546/12484
– Jon Schneider
Aug 9 at 22:07
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What online brokers offer APIs? [closed]
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IB does seem to be the best option, and so far the only one with a wide range of language support.
– Wilco
Sep 29 '08 at 15:42
1
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Checking if a folder exists using a .bat file [closed]
...he name of your file.
For a directory look at this https://jeffpar.github.io/kbarchive/kb/065/Q65994/
C:
IF NOT EXIST C:\WIN\ GOTO NOWINDIR
CD \WIN
:NOWINDIR
trailing backslash ('\') seems to be enough to distinguish between directories and ordinary files.
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