大约有 44,000 项符合查询结果（耗时：0.0598秒） [XML]
Detecting an undefined object property
... check if an object does not actually have such a property, and will therefore return undefined by default when you try and access it:
if(!o.hasOwnProperty('myProperty')) {
alert("myProperty does not exist");
}
To check if the value associated with an identifier is the special value undefined, ...
Android SQLite DB When to Close
I am working with a SQLite database on android. My database manager is a singleton and right now opens a connection to the database when it is initialized. It is safe to leave the database open the entire time so that when someone calls my class to work with the database it is already open? Or shoul...
PHP equivalent of .NET/Java's toString()
...
You can use the casting operators:
$myText = (string)$myVar;
There are more details for string casting and conversion in the Strings section of the PHP manual, including special handling for booleans and nulls.
...
How can I reset or revert a file to a specific revision?
...ash of the commit you want is c5f567:
git checkout c5f567 -- file1/to/restore file2/to/restore
The git checkout man page gives more information.
If you want to revert to the commit before c5f567, append ~1 (where 1 is the number of commits you want to go back, it can be anything):
git checkout ...
compareTo() vs. equals()
When testing for equality of String 's in Java I have always used equals() because to me this seems to be the most natural method for it. After all, its name already says what it is intended to do. However, a colleague of mine recently told me had been taught to use compareTo() == 0 instead of ...
Utility classes are evil? [closed]
...actly evil, but they can violate the principles that compose a good object-oriented design. In a good object-oriented design, most classes should represent a single thing and all of its attributes and operations. If you are operating on a thing, that method should probably be a member of that thing....
Lock-free multi-threading is for real threading experts
...operation
retry if it fails
(*optional: depends on the data structure/algorithm)
The last bit is eerily similar to a spinlock. In fact, it is a basic spinlock. :)
I agree with @nobugz on this: the cost of the interlocked operations used in lock-free multi-threading is dominated by the cache and m...
Greedy vs. Reluctant vs. Possessive Quantifiers
I found this excellent tutorial on regular expressions and while I intuitively understand what "greedy", "reluctant" and "possessive" quantifiers do, there seems to be a serious hole in my understanding.
...
git: Switch branch and ignore any changes without committing
I was working on a git branch and was ready to commit my changes, so I made a commit with a useful commit message. I then absentmindedly made minor changes to the code that are not worth keeping. I now want to change branches, but git gives me,
...
Cookie blocked/not saved in IFRAME in Internet Explorer
...therexample.net/page.html , I have an IFRAME SRC="http://example.com/someform.asp" . That IFRAME displays a form for the user to fill out and submit to http://example.com/process.asp . When I open the form (" someform.asp ") in its own browser window, all works well.
However, when I load someform...