大约有 40,000 项符合查询结果（耗时：0.0238秒） [XML]
Best way to serialize an NSData into a hexadeximal string
... string of NSData. Empty string if data is empty. */
const unsigned char *dataBuffer = (const unsigned char *)[self bytes];
if (!dataBuffer)
return [NSString string];
NSUInteger dataLength = [self length];
NSMutableString *hexString = [NSMutableString stri...
What does int argc, char *argv[] mean?
...ention, but they can be given any valid identifier: int main(int num_args, char** arg_strings) is equally valid.
They can also be omitted entirely, yielding int main(), if you do not intend to process command line arguments.
Try the following program:
#include <iostream>
int main(int argc,...
What is the difference between static_cast and C style casting?
...situations where all that is needed is a simple conversion. The ability to select between several different casting operators of differing degrees of power can prevent programmers from inadvertently casting to an incorrect type.
...
How to display unique records from a has_many through relationship?
...r the SQL DISTINCT stmt (e.g. has_many :products, :through => :orders, :select => "DISTINCT products.*). In the first case, ALL records are fetched and rails removes the duplicates for you. In the later case, only non-duplicate records are fetched from the db so it might offer better performan...
Difference between BYTE and CHAR in column datatypes
...
Let us assume the database character set is UTF-8, which is the recommended setting in recent versions of Oracle. In this case, some characters take more than 1 byte to store in the database.
If you define the field as VARCHAR2(11 BYTE), Oracle can us...
What belongs in an educational tool to demonstrate the unwarranted assumptions people make in C/C++?
...lo"); /* printf() returns the number of
characters successfully printed by it
*/
}
int World()
{
return printf("World !");
}
int main()
{
int a = Hello() + World(); //might print Hello World! or World! Hell...
Turn a string into a valid filename?
I have a string that I want to use as a filename, so I want to remove all characters that wouldn't be allowed in filenames, using Python.
...
Differences between C++ string == and compare()?
...ard has to say about operator==
21.4.8.2 operator==
template<class charT, class traits, class Allocator>
bool operator==(const basic_string<charT,traits,Allocator>& lhs,
const basic_string<charT,traits,Allocator>& rhs) noexcept;
Returns: lhs.compa...
scp or sftp copy multiple files with single command
...
Copy multiple files from remote to local:
$ scp your_username@remote.edu:/some/remote/directory/\{a,b,c\} ./
Copy multiple files from local to remote:
$ scp foo.txt bar.txt your_username@remotehost.edu:~
$ scp {foo,bar}.txt your_u...
PreparedStatement IN clause alternatives?
... and cons of each is available here.
The suggested options are:
Prepare SELECT my_column FROM my_table WHERE search_column = ?, execute it for each value and UNION the results client-side. Requires only one prepared statement. Slow and painful.
Prepare SELECT my_column FROM my_table WHERE search_...