大约有 44,000 项符合查询结果（耗时：0.0641秒） [XML]
How to Deal with Temporary NSManagedObject instances?
I need to create NSManagedObject instances, do some stuff with them and then trash them or store to sqlite db. The problem is, I cannot create instances of NSManagedObject unconnected to NSManagedObjectContext and this means I have to clear up somehow after I decide that I don't need some of ...
Is null an Object?
...case - any method invocation on a null results in a NullPointerException.
And this is what the Java Language Specification has to say on this topic:
There is also a special null type, the
type of the expression null, which has
no name. Because the null type has no
name, it is impossible t...
R object identification
... often ending up with a function producing output for which I don't understand the output data type. I'm expecting a list and it ends up being a list of lists or a data frame or something else. What's a good method or workflow for figuring out the output data type when first using a function?
...
Why are Oracle table/column/index names limited to 30 characters?
I can understand that many years ago there would be this kind of limitation, but nowadays surely this limit could easily be increased. We have naming conventions for objects, but there is always a case that turns up where we hit this limit - especially in naming foreign keys.
...
MySQL Fire Trigger for both Insert and Update
Is it possible to fire a mysql trigger for both the insert and update events of a table?
3 Answers
...
data.frame rows to a list
...
Like this:
xy.list <- split(xy.df, seq(nrow(xy.df)))
And if you want the rownames of xy.df to be the names of the output list, you can do:
xy.list <- setNames(split(xy.df, seq(nrow(xy.df))), rownames(xy.df))
...
Format LocalDateTime with Timezone in Java8
...ern symbol Z). So the formatter tries to access an unavailable information and has to throw the exception you observed.
Solution:
Use a type which has such an offset or timezone information. In JSR-310 this is either OffsetDateTime (which contains an offset but not a timezone including DST-rules)...
Why can tuples contain mutable items?
...ghts to help complete your mental model of what tuples are, how they work, and their intended use:
Tuples are characterized less by their immutability and more by their intended purpose.
Tuples are Python's way of collecting heterogeneous pieces of information under one roof. For example,
s = ('...
How Can I Set the Default Value of a Timestamp Column to the Current Timestamp with Laravel Migratio
...r/Migrations. I have gone through the Laravel documentation several times, and I don't see how I can make that the default for a timestamp column.
...
How to convert Linux cron jobs to “the Amazon way”?
...s their response:
Tom
I did a quick poll of some of my colleagues and came up empty on the
cron, but after sleeping on it I realised the important step may be
limited to locking. So I looked for "distributed cron job locking"
and found a reference to Zookeeper, an Apache project.
...