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Do I set properties to nil in dealloc when using ARC?
...
@zeiteisen: No. unsafe_unretained is exactly equivalent to an assign property and is the normal behavior for delegate relationships under MRR, and these need to be nilled out.
– Lily Ballard
Mar 7 '12 at 20:2...
How to check if a variable is a dictionary in Python?
...t, defaultdict, or Counter from the collections module:
if isinstance(any_object, dict):
But there are even more flexible options.
Supporting abstractions:
from collections.abc import Mapping
if isinstance(any_object, Mapping):
This allows the user of your code to use their own custom implem...
What does `:_*` (colon underscore star) do in Scala?
...to the method with repeated parameters (as denoted with Node* above).
The _* type annotation is covered in "4.6.2 Repeated Parameters" of the SLS.
The last value parameter of a parameter section may be suffixed by “*”, e.g. (..., x:T *). The type of such a repeated parameter inside th...
Backup/Restore a dockerized PostgreSQL database
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Backup your databases
docker exec -t your-db-container pg_dumpall -c -U postgres > dump_`date +%d-%m-%Y"_"%H_%M_%S`.sql
Restore your databases
cat your_dump.sql | docker exec -i your-db-container psql -U postgres
...
What is the maximum recursion depth in Python, and how to increase it?
...mple context manager like this:
import sys
class recursionlimit:
def __init__(self, limit):
self.limit = limit
self.old_limit = sys.getrecursionlimit()
def __enter__(self):
sys.setrecursionlimit(self.limit)
def __exit__(self, type, value, tb):
sys.setr...
How do I partially update an object in MongoDB so the new object will overlay / merge with the exist
...e data then?
You know you can do the following:
db.collection.update( { _id:...} , { $set: someObjectWithNewData }
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In Scala, what exactly does 'val a: A = _' (underscore) mean?
What exactly does val a: A = _ initialize a value to? Is this a typed null? Thanks.
2 Answers
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低功耗蓝牙内置版使用指导 · App Inventor 2 中文网
...。
案例一：按名称连接设备
when 按钮_连接.Click() {
BluetoothLowEnergy1.ConnectMatchingName(文本输入框_设备名称.Text)
}
when BluetoothLowEnergy1.Connected() {
标签1.Text = "已连接"
}
when BluetoothLowEnergy1.ConnectionFailed(原因) {
标...
How to copy a row and insert in same table with a autoincrement field in MySQL?
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Use INSERT ... SELECT:
insert into your_table (c1, c2, ...)
select c1, c2, ...
from your_table
where id = 1
where c1, c2, ... are all the columns except id. If you want to explicitly insert with an id of 2 then include that in your INSERT column list and your SE...
c#: getter/setter
...ate the equivalent of the following simple implementation:
private string _type;
public string Type
{
get { return _type; }
set { _type = value; }
}
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