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App Inventor 2 实现上传文件到服务器全方案总结 · App Inventor 2 中文网
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php服务端代码参考：
python服务端参考：
from flask_restful import Api, Resource
from flask import Flask, request
app = Flask(__name__)
api = Api(app)
# 这边的类名是自己定义的
class receive_pic(Resource):
def put(self):
#接收二进制流保存为图...
Is it possible to make the -init method private in Objective-C?
...
NS_UNAVAILABLE
- (instancetype)init NS_UNAVAILABLE;
This is a the short version of the unavailable attribute. It first appeared in macOS 10.7 and iOS 5. It is defined in NSObjCRuntime.h as #define NS_UNAVAILABLE UNAVAILABLE_...
What are the applications of binary trees?
...oving from one level to the next requires one comparison, and there are log_2(m) levels, for a total of log_2(m) comparisons.
In contrast, an n-ary tree will require log_2(n) comparisons (using a binary search) to move to the next level. Since there are log_n(m) total levels, the search will requi...
Check if a JavaScript string is a URL
...{1,3}\\.){3}\\d{1,3}))'+ // OR ip (v4) address
'(\\:\\d+)?(\\/[-a-z\\d%_.~+]*)*'+ // port and path
'(\\?[;&a-z\\d%_.~+=-]*)?'+ // query string
'(\\#[-a-z\\d_]*)?$','i'); // fragment locator
return !!pattern.test(str);
}
...
How to measure time in milliseconds using ANSI C?
...on many systems.
You can use this function like this:
struct timeval tval_before, tval_after, tval_result;
gettimeofday(&tval_before, NULL);
// Some code you want to time, for example:
sleep(1);
gettimeofday(&tval_after, NULL);
timersub(&tval_after, &tval_before, &tval_resu...
Do I need to explicitly call the base virtual destructor?
...of concept with results:
class base {
public:
base() { cout << __FUNCTION__ << endl; }
~base() { cout << __FUNCTION__ << endl; }
};
class derived : public base {
public:
derived() { cout << __FUNCTION__ << endl; }
~derived() { cout << __FU...
Delete column from SQLite table
...trate how this could be done:
BEGIN TRANSACTION;
CREATE TEMPORARY TABLE t1_backup(a,b);
INSERT INTO t1_backup SELECT a,b FROM t1;
DROP TABLE t1;
CREATE TABLE t1(a,b);
INSERT INTO t1 SELECT a,b FROM t1_backup;
DROP TABLE t1_backup;
COMMIT;
...
Measuring elapsed time with the Time module
...
start_time = time.time()
# your code
elapsed_time = time.time() - start_time
You can also write simple decorator to simplify measurement of execution time of various functions:
import time
from functools import wraps
PROF_DATA...
Scala type programming resources
...ample (taken from metascala and apocalisp):
sealed trait Nat
sealed trait _0 extends Nat
sealed trait Succ[N <: Nat] extends Nat
Here you have a peano encoding of the natural numbers. That is, you have a type for each non-negative integer: a special type for 0, namely _0; and each integer grea...
How do you get assembler output from C/C++ source in gcc?
.... The output file can be still be set by using the -o option.
gcc -S -o my_asm_output.s helloworld.c
Of course this only works if you have the original source.
An alternative if you only have the resultant object file is to use objdump, by setting the --disassemble option (or -d for the abbreviat...