大约有 49,000 项符合查询结果（耗时：0.1175秒） [XML]
Checking if a folder exists (and creating folders) in Qt, C++
In Qt, how do I check if a given folder exists in the current directory?
If it doesn't exist, how do I then create an empty folder?
...
How to express a NOT IN query with ActiveRecord/Rails?
Just to update this since it seems a lot of people come to this, if you are using Rails 4 look at the answers by Trung Lê` and VinniVidiVicci.
...
multiprocessing.Pool: When to use apply, apply_async or map?
...rast to Pool.apply, the Pool.apply_async method also has a callback which, if supplied, is called when the function is complete. This can be used instead of calling get().
For example:
import multiprocessing as mp
import time
def foo_pool(x):
time.sleep(2)
return x*x
result_list = []
def...
Android dismiss keyboard
...
You want to disable or dismiss a virtual Keyboard?
If you want to just dismiss it you can use the following lines of code in your button's on click Event
InputMethodManager imm = (InputMethodManager)getSystemService(Context.INPUT_METHOD_SERVICE);
imm.hideSoftInputFromWindow(...
Switch statement for greater-than/less-than
...------
1.0 time 37ms 73ms 68ms 184ms 73ms 21ms
if-immediate 1.0 1.0 1.0 2.6 1.0 1.0
if-indirect 1.2 1.8 3.3 3.8 2.6 1.0
switch-immediate 2.0 1.1 2.0 1.0 2.8 1.3
switch-range ...
Insert a line at specific line number with sed or awk
I have a script file which I need to modify with another script to insert a text at the 8th line.
9 Answers
...
Adding a public key to ~/.ssh/authorized_keys does not log me in automatically
...
You need to verify the permissions of the authorized_keys file and the folder / parent folders in which it is located.
chmod 700 ~/.ssh
chmod 600 ~/.ssh/authorized_keys
For more information see this page.
You may also need to change/ver...
Dynamically select data frame columns using $ and a character value
I have a vector of different column names and I want to be able to loop over each of them to extract that column from a data.frame. For example, consider the data set mtcars and some variable names stored in a character vector cols . When I try to select a variable from mtcars using a dynamic s...
How do I use a file grep comparison inside a bash if/else statement?
...
From grep --help, but also see man grep:
Exit status is 0 if any line was selected, 1 otherwise;
if any error occurs and -q was not given, the exit status is 2.
if grep --quiet MYSQL_ROLE=master /etc/aws/hosts.conf; then
echo exists
else
echo not found
fi
You may want to u...
How do I fix a NoSuchMethodError?
...
Without any more information it is difficult to pinpoint the problem, but the root cause is that you most likely have compiled a class against a different version of the class that is missing a method, than the one you are using when running it.
Look at the st...