在Xcode的Foundation框架中,NSFormatter只是一個抽象類，我們平常用到的是它的兩個子類：NSNumberFormatter、NSDateFormatter,本篇先介紹NSNumberFormatter,NSDateFormatter會在下一篇進行介紹.
使用NSNumberFormatter可以將NSNumber轉化成自己想要的格式來進行輸出,同時NSNumberFormatter也支持使用NSString 類型的對象轉換為NSNumber類型的對象
NSNumberFormatter支持的枚舉類型如下,具體對應什么類型我會在代碼里進行解釋
typedef CF_ENUM(CFIndex, CFNumberFormatterStyle) { // number format styles
kCFNumberFormatterNoStyle = 0,
kCFNumberFormatterDecimalStyle = 1,
kCFNumberFormatterCurrencyStyle = 2,
kCFNumberFormatterPercentStyle = 3,
kCFNumberFormatterScientificStyle = 4,
kCFNumberFormatterSpellOutStyle = 5,
kCFNumberFormatterOrdinalStyle CF_ENUM_AVAILABLE(10_11, 9_0) = 6,
kCFNumberFormatterCurrencyISOCodeStyle CF_ENUM_AVAILABLE(10_11, 9_0) = 8,
kCFNumberFormatterCurrencyPluralStyle CF_ENUM_AVAILABLE(10_11, 9_0) = 9,
kCFNumberFormatterCurrencyAccountingStyle CF_ENUM_AVAILABLE(10_11, 9_0) = 10,
};
使用方法一般如下:
一.使用NSNumber轉化成自己想要的格式來進行輸出
1.先創建一個NSNumerFormatter對象
NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
2.創建一個NSNumber對象
NSNumber *number = [NSNumber numberWithDouble:12345.655521];
3.設置NSNumberFomatter的枚舉值類型,
formatter1.numberStyle = kCFNumberFormatterNoStyle; //去掉小數點 四舍五入保留整數 12346
4.調用NSNumberFormatter的實例方法將NSNumebr對象轉換為字符串格式:
NSString *strOfFormatter =[formatter stringFromNumber:number];
5.將該字符串輸出
NSLog(@"%@",strOfFormatter);
下面我寫了一個例子,僅供大家參考:
NSNumberFormatter *formatter1 = [[NSNumberFormatter alloc] init];
NSNumberFormatter *formatter2 = [[NSNumberFormatter alloc] init];
NSNumberFormatter *formatter3 = [[NSNumberFormatter alloc] init];
NSNumberFormatter *formatter4 = [[NSNumberFormatter alloc] init];
NSNumberFormatter *formatter5 = [[NSNumberFormatter alloc] init];
NSNumberFormatter *formatter6 = [[NSNumberFormatter alloc] init];
NSNumberFormatter *formatter7 = [[NSNumberFormatter alloc] init];
NSNumberFormatter *formatter8 = [[NSNumberFormatter alloc] init];
NSNumberFormatter *formatter9 = [[NSNumberFormatter alloc] init];
NSNumberFormatter *formatter10 = [[NSNumberFormatter alloc] init];
//原值 12345.655521
formatter1.numberStyle = kCFNumberFormatterNoStyle; //去掉小數點 四舍五入保留整數 12346
formatter2.numberStyle = NSNumberFormatterDecimalStyle; //以國際化格式輸出 保留三位小數,第四位小數四舍五入 12,345.66
formatter3.numberStyle = kCFNumberFormatterCurrencyStyle; //以貨幣通用格式輸出 保留2位小數,第三位小數四舍五入,在前面添加dollor符號 $12,345.66
formatter4.numberStyle = kCFNumberFormatterPercentStyle; //以百分制形式輸出 整個數字乘以保留2為小數,第三位小數四舍五入,然后乘以100,同時在最后加上百分號
formatter5.numberStyle = kCFNumberFormatterScientificStyle; //以科學計數法輸出 1.2345655521E4
formatter6.numberStyle = kCFNumberFormatterSpellOutStyle; //原值英文表示,
// 正常來說應該輸出 twelve thousand, three hundred and forty-five point six five five five two one
//實際輸出 twelve thousand three hundred forty-five point six five five five two one
//少了一個and ,這個跟系統設置的區域語言有關系
//還有其他的四種返回格式
formatter7.numberStyle = kCFNumberFormatterOrdinalStyle; //輸出 12,346th
formatter8.numberStyle = kCFNumberFormatterCurrencyISOCodeStyle;//輸出 USD12,345.66
formatter9.numberStyle = kCFNumberFormatterCurrencyPluralStyle;//輸出 12,345.66 US dollars
formatter10.numberStyle = kCFNumberFormatterCurrencyAccountingStyle;//輸出 $12,345.66
NSNumber *number = [NSNumber numberWithDouble:12345.655521];
NSLog(@"kCFNumberFormatterNoStyle=%@", [formatter1 stringFromNumber:number]);
NSLog(@"NSNumberFormatterDecimalStyle=%@", [formatter2 stringFromNumber:number]);
NSLog(@"kCFNumberFormatterCurrencyStyle=%@", [formatter3 stringFromNumber:number]);
NSLog(@"kCFNumberFormatterPercentStyle=%@", [formatter4 stringFromNumber:number]);
NSLog(@"kCFNumberFormatterScientificStyle=%@", [formatter5 stringFromNumber:number]);
NSLog(@"kCFNumberFormatterSpellOutStyle=%@", [formatter6 stringFromNumber:number]);
NSLog(@"kCFNumberFormatterOrdinalStyle=%@", [formatter7 stringFromNumber:number]);
NSLog(@"kCFNumberFormatterCurrencyISOCodeStyle=%@", [formatter8 stringFromNumber:number]);
NSLog(@"kCFNumberFormatterCurrencyPluralStyle=%@", [formatter9 stringFromNumber:number]);
NSLog(@"kCFNumberFormatterCurrencyAccountingStyle=%@", [formatter10 stringFromNumber:number]);
輸出結果如下:
2016-01-30 18:43:22.169 Test_NFNumberFormatter[1210:29952] kCFNumberFormatterNoStyle=12346
2016-01-30 18:43:22.170 Test_NFNumberFormatter[1210:29952] NSNumberFormatterDecimalStyle=12,345.656
2016-01-30 18:43:22.171 Test_NFNumberFormatter[1210:29952] kCFNumberFormatterCurrencyStyle=$12,345.66
2016-01-30 18:43:22.171 Test_NFNumberFormatter[1210:29952] kCFNumberFormatterPercentStyle=1,234,566%
2016-01-30 18:43:22.171 Test_NFNumberFormatter[1210:29952] kCFNumberFormatterScientificStyle=1.2345655521E4
2016-01-30 18:43:22.172 Test_NFNumberFormatter[1210:29952] kCFNumberFormatterSpellOutStyle=twelve thousand three hundred forty-five point six five five five two one
2016-01-30 18:43:22.172 Test_NFNumberFormatter[1210:29952] kCFNumberFormatterOrdinalStyle=12,346th
2016-01-30 18:43:22.173 Test_NFNumberFormatter[1210:29952] kCFNumberFormatterCurrencyISOCodeStyle=USD12,345.66
2016-01-30 18:43:22.173 Test_NFNumberFormatter[1210:29952] kCFNumberFormatterCurrencyPluralStyle=12,345.66 US dollars
2016-01-30 18:43:22.173 Test_NFNumberFormatter[1210:29952] kCFNumberFormatterCurrencyAccountingStyle=$12,345.66
二.使用NSString 類型的對象轉換為NSNumber類型的對象
因為轉化方式大同小異,所以我就接着上面的代碼寫了:
/*
同時,NSNumberFomatter也支持從NSString類型的對象轉為NSNumber類型的對象
現在拿formatter1和formatter2來舉例
先拿到NSString格式的數字
*/
NSString *strOfFormatter1 = [formatter1 stringFromNumber:number];
NSString *strOfFormatter2 = [formatter2 stringFromNumber:number];
// 目前 strOfFormatter1 = 12346
// strOfFormatter2 = 12,345.656
//轉化為NSNumber格式
NSNumber *number1 = [formatter1 numberFromString:strOfFormatter1];
NSNumber *number2 = [formatter2 numberFromString:strOfFormatter2];
//打印number
NSLog(@"number1=%@",number1);
NSLog(@"number2=%@",number2);
輸出結果為:
2016-01-30 19:24:47.400 Test_NFNumberFormatter[1335:49384] number1=12346
2016-01-30 19:24:47.943 Test_NFNumberFormatter[1335:49384] number2=12345.656
總結:NSNumberFormatter可以讓我們方便的在NSString和NSNumber之間進行轉化,當我們需要轉化成一些特殊的格式的時候,這無疑給我們提供了很大的便利.文中提到的有個別格式是講數字以通用的描述文字輸出,文中輸出的是twelve thousand three hundred forty-five point six five five five two one,這個是跟我們設置的區域語言參數有關系的,如果我們設置的是China,輸出的文字就將會是中文的.(有人說通過在Info.plist文件中的字段Localization native development region設置的,設置為China就好了)但是我發現設置完之后還是沒有辦法打印出來中文的格式,各位可以自己試試.