ios 學習筆記 2

1. NSUserDefaults

　　個人認為ios這個方法有點類似於c#中Properties.Settings.Default，NSUserDefaults只支援： NSString, NSNumber, NSDate, NSArray, NSDictionary.

　　建立一個user defaults方法有多個，最簡單得快速建立方法:

   　NSUserDefaults *accountDefaults = [NSUserDefaults standardUserDefaults];
　　添加資料到 user defaults:
　　[accountDefaults setObject:nameField.text forKey:UserDefaultNameKey];
　　也可以添加基礎資料型別 (Elementary Data Type)int, float, bool等，有相應得方法
　　[accountDefaults setBool:YES forKey:UserDefaultBoolKey];
　　從user defaults中擷取資料:
　　[accountDefaults objectForKey:NCUserDefaultNameKey]
　　[accountDefaults boolForKey: UserDefaultBoolKey];
     針對同一個關鍵字對應的對象或者資料，可以對它進行重寫，重寫之後關鍵字就對應新的對象或者資料，舊的對象或者資料會被自動清理。

2. NSDateFormatter
　　格式化日期文字，copy一份常用參數：

a: AM/PM (上午/下午)

A: 0~86399999 (一天的第A微秒)

c/cc: 1~7 (一周的第一天, 周天為1)

ccc: Sun/Mon/Tue/Wed/Thu/Fri/Sat (星期幾簡寫)

cccc: Sunday/Monday/Tuesday/Wednesday/Thursday/Friday/Saturday (星期幾全拼)

d: 1~31 (月份的第幾天, 帶0)

D: 1~366 (年份的第幾天,帶0)

e: 1~7 (一周的第幾天, 帶0)

E~EEE: Sun/Mon/Tue/Wed/Thu/Fri/Sat (星期幾簡寫)

EEEE: Sunday/Monday/Tuesday/Wednesday/Thursday/Friday/Saturday (星期幾全拼)

F: 1~5 (每月的第幾周, 一周的第一天為周一)

g: Julian Day Number (number of days since 4713 BC January 1) 未知

G~GGG: BC/AD (Era Designator Abbreviated) 未知

GGGG: Before Christ/Anno Domini 未知

h: 1~12 (0 padded Hour (12hr)) 帶0的時, 12小時制

H: 0~23 (0 padded Hour (24hr))  帶0的時, 24小時制

k: 1~24 (0 padded Hour (24hr) 帶0的時, 24小時制

K: 0~11 (0 padded Hour (12hr)) 帶0的時, 12小時制

L/LL: 1~12 (0 padded Month)  第幾月

LLL: Jan/Feb/Mar/Apr/May/Jun/Jul/Aug/Sep/Oct/Nov/Dec 月份簡寫

LLLL: January/February/March/April/May/June/July/August/September/October/November/December 月份全稱

m: 0~59 (0 padded Minute) 分鐘

M/MM: 1~12 (0 padded Month) 第幾月

MMM: Jan/Feb/Mar/Apr/May/Jun/Jul/Aug/Sep/Oct/Nov/Dec

MMMM: January/February/March/April/May/June/July/August/September/October/November/December

q/qq: 1~4 (0 padded Quarter) 第幾季度

qqq: Q1/Q2/Q3/Q4 季度簡寫

qqqq: 1st quarter/2nd quarter/3rd quarter/4th quarter 季度全拼

Q/QQ: 1~4 (0 padded Quarter) 同小寫

QQQ: Q1/Q2/Q3/Q4 同小寫

QQQQ: 1st quarter/2nd quarter/3rd quarter/4th quarter 同小寫

s: 0~59 (0 padded Second) 秒數

S: (rounded Sub-Second) 未知

u: (0 padded Year) 未知

v~vvv: (General GMT Timezone Abbreviation) 常規GMT時區的編寫

vvvv: (General GMT Timezone Name) 常規GMT時區的名稱

w: 1~53 (0 padded Week of Year, 1st day of week = Sunday, NB: 1st week of year starts from the last Sunday of last year) 一年的第幾周, 一周的開始為周日,第一周從去年的最後一個周日起算

W: 1~5 (0 padded Week of Month, 1st day of week = Sunday) 一個月的第幾周

y/yyyy: (Full Year) 完整的年份

yy/yyy: (2 Digits Year)  2個數位年份

Y/YYYY: (Full Year, starting from the Sunday of the 1st week of year) 這個年份未知幹嘛用的

YY/YYY: (2 Digits Year, starting from the Sunday of the 1st week of year) 這個年份未知幹嘛用的

z~zzz: (Specific GMT Timezone Abbreviation) 指定GMT時區的編寫

zzzz: (Specific GMT Timezone Name) Z: +0000 (RFC 822 Timezone) 指定GMT時區的名稱

 

執行個體：
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setAMSymbol:@"AM"];
[formatter setPMSymbol:@"PM"];
[formatter setDateFormat:@"MM/dd/yyyy hh:mm:a"];
 // [NSString stringWithFormat:@"Last Updated: %@", [formatter stringFromDate:[NSDate date]]];

 

3. backgroundView

　　UIView* backgroundView= = [[TESTCellView alloc] initWithFrame:CGRectZero];

　　backgroundView.opaque = YES;
      backgroundView.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"list-gap.png"]];
      backgroundView = backgroundView;
      [backgroundView release];

 

4. NSParameterAssert

　　字面意思是帶參數的斷點，條件為假時執行，主要用於程式調試

　　NSParameterAssert( 1== 2 );

 

5. Reachability

　　類似於一個網路狀況的探針。

　　[[NSNotificationCenter defaultCenter] addObserver: self selector: @selector(reachabilityChanged:) name: kReachabilityChangedNotification object: nil];
    
    hostReach = [[Reachability reachabilityWithHostName: @"hubj.cnblogs.com"] retain];
    [hostReach startNotifier];
    
    wifiReach=[[Reachability reachabilityForLocalWiFi]retain];
    [wifiReach startNotifier];

 

- (void)reachabilityChanged: (NSNotification* )note {
    Reachability* curReach = [note object];
    NSParameterAssert([curReach isKindOfClass: [Reachability class]]);
    
    NetworkStatus netStatus = [curReach currentReachabilityStatus];
    
    switch (netStatus)
    {
        case NotReachable:
        {
            NSLog(@"Access Not Available");
            break;
        }
            
        case ReachableViaWWAN:
        {
            NSLog(@"Reachable WWAN");
            break;
        }
        case ReachableViaWiFi:
        {
            NSLog(@"Reachable WiFi");
            break;
        }
    }

}