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differentiate null=True, blank=True in django
...o need your database to allow NULL values for that field. The exception is CharFields and TextFields, which in Django are never saved as NULL. Blank values are stored in the DB as an empty string ('').
A few examples:
models.DateTimeField(blank=True) # raises IntegrityError if blank
models.DateTi...
How to use glOrtho() in OpenGL?
...0, 1.5, 20.0);
}
glMatrixMode(GL_MODELVIEW);
}
int main(int argc, char** argv) {
glutInit(&argc, argv);
if (argc > 1) {
ortho = 1;
}
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
glutInitWindowSize(500, 500);
glutInitWindowPosition(100, 100);
glutCr...
What are Unwind segues for and how do you use them?
...e want to unwind to Red from Green when the button is pressed:
You must select the action which is defined in the view controller you want to unwind to:
You can also unwind to Red from Blue (which is "two steps away" in the navigation stack). The key is selecting the correct unwind action.
Be...
What's the best way to check if a file exists in C?
...t; // stat
#include <stdbool.h> // bool type
bool file_exists (char *filename) {
struct stat buffer;
return (stat (filename, &buffer) == 0);
}
and call it like this:
#include <stdio.h> // printf
int main(int ac, char **av) {
if (ac != 2)
return 1;
...
XML attribute vs XML element
...as a > or < you XML document will break I think there are five ascii chars (>, <, &, ?,") that will kill it. If this special character was in an Element you can simply add some CDATA tags around this data. I would say, only use attributes when you 100% know what values are going t...
How do you copy and paste into Git Bash
...
With QuickEdit on this becomes pretty easy: select, Enter, Insert
– gphilip
Feb 10 '14 at 8:49
3
...
How to evaluate a math expression given in string form?
...r) {
return new Object() {
int pos = -1, ch;
void nextChar() {
ch = (++pos < str.length()) ? str.charAt(pos) : -1;
}
boolean eat(int charToEat) {
while (ch == ' ') nextChar();
if (ch == charToEat) {
nextChar...
Null coalescing in powershell
...ll values in the same order as the array created in Step 1.
[0] is used to select the first element of the filtered array.
Simplifying that:
Create an array of possible values, in preferred order
Exclude all null values from the array
Take the first item from the resulting array
Caveats
Unlik...
Python in Xcode 4+?
...
In the menu bar, click “File” → “New” → “New Project…”.
Select “Other” in the left pane, then "External Build System" in the right page, and next click "Next".
Enter the product name, organization name, or organization identifier.
For the “Build Tool” field, type in /usr/l...
Why doesn't “System.out.println” work in Android?
... throws IOException{
if(mCache == null) mCache = "";
if(((char) b) == '\n'){
Log.i("redirect from system.out", mCache);
mCache = "";
}else{
mCache += (char) b;
}
}
}
...