eJamesLin

    NSString *str = @"abca";
    NSLog(@"%@", [str substringWithRange:NSMakeRange(0, 1)]); // "a"
    NSLog(@"%@", [str substringWithRange:NSMakeRange(0, 3)]); // "abc"
    NSLog(@"%@", [str substringWithRange:NSMakeRange(0, 4)]); // "abca"

    unichar a = [str characterAtIndex:0];
    unichar a3 = [str characterAtIndex:3];

    NSLog(@"%C", a);
    if (a == a3) { NSLog(@"equal"); }

eJamesLin

    // 
    NSMutableArray *array = [[NSMutableArray alloc] initWithCapacity:1];
    array[0] = @"0";
    array[1] = @"1"; // won't crash... but not good

    // C array, cannot be used as property
    NSInteger matrix[3][3];
    matrix[0][0] = 10;
    NSLog(@"%s %@", __PRETTY_FUNCTION__, array);
    NSLog(@"%s %ld", __PRETTY_FUNCTION__, matrix[0][0]); //10

eJamesLin

extension String {
    /*
     Ref: http://oleb.net/blog/2014/07/swift-strings/
     "Because of the way Swift strings are stored, the String type does not support random access to its Characters via an integer index — there is no direct equivalent to NSStringʼs characterAtIndex: method. Conceptually, a String can be seen as a doubly linked list of characters rather than an array."

     By creating and storing a seperate array of the same sequence of characters,
     we could hopefully achieve amortized O(1) time for random access.
     */
    func randomAccessCharactersArray() -> [Character] {
        return Array(self.characters)

eJamesLin

# Version: 1.3
# Author: pantuts
# Description: Parse URLs in Youtube User's Playlist (Video Playlist not Favorites)
# Use python3 and later
# Agreement: You can use, modify, or redistribute this tool under
# the terms of GNU General Public License (GPLv3).
# This tool is for educational purposes only. Any damage you make will not affect the author.
# Usage: python3 youParse.py youtubeURLhere
 
import re