ObjectC----幾個常用的類

ObjectC----幾個常用的類

// Create By 郭仔 2015年03月31日20:54:20

1. NSString類

 

 

// 求字符串長度

NSString *str = @"Hello郭String";

NSUInteger len = [str length]; // NSUInterger即long

NSLog(@"%ld",len);

 

//獲取子字符串

 

 

NSString *substr = [str substringFromIndex:5];//從下標5開始取子字符串

NSLog(@"%@",substr);

// 從開始取子字符串到下標為5的位置截止

NSString *substr2 = [str substringToIndex:5];

NSLog(@"%@",substr2);

 

NSRange rang = {2,3}; //起始位置和長度

// 從起始位置2取長度為3的子字符串

NSString *substr3 = [str substringWithRange:rang];

NSLog(@"%@",substr3);

 

//拼接字符串

 

NSString *comStr1 = [str stringByAppendingString:@"IOS"];

NSLog(@"%@",comStr1);

 

NSString *comStr2 = [str stringByAppendingFormat:@"hehe%@ %@",@"hhh",@"jjj"];

NSLog(@"%@",comStr2);

 

 

//字符串替換

 

NSString * newStr1 = [str stringByReplacingOccurrencesOfString:@"string" withString:@"world"];

NSLog(@"%@",newStr1);

 

 

// 判斷字符串是否相等

//判斷字符串是否相等用 isEqualTo方法，不能用==判斷

// isEqualTo方法判斷的時字符串的內容是否相等，而==判斷的時兩個指針是否指向同一地址

 

NSString *cmpStr = @"Hello String";

BOOL eq = [str isEqualToString:cmpStr];

if (eq) {

NSLog(@"相等");

}

else{

NSLog(@"不相等");

}

// 判斷前綴是否已給定的字符串相等，即是否已該字符串開頭

BOOL prefix = [str hasPrefix:@"Hello"];

if (prefix) {

NSLog(@"以Hello開頭");

}

else {

NSLog(@"不以Hello開頭");

}

 

 

 

//判斷後綴

//判斷是否已png結尾，是就替換成jpg,否則拼接jpg

BOOL isPng = [str hasSuffix:@"png"];

if (isPng) {

//執行替換

NSString * tem = [str stringByReplacingOccurrencesOfString:@"png" withString:@"jpg"];

NSLog(@"%@",tem);

}

else

{ //執行拼接jpg

NSString *tem = [str stringByAppendingString:@"jpg"];

NSLog(@"%@",tem);

}

 

 

 

=====================================================================================

2. NSMutableString//可變字符串

NSMutableString *mulStr = [NSMutableString stringWithString:@"Hello"];

NSLog(@"%@",mulStr);

 

//拼接

[mulStr appendFormat:@"guozai"];

NSLog(@"%@",mulStr);

[mulStr appendString:@"mutible"];

NSLog(@"%@",mulStr);

 

 

//刪除子字符串

NSRange ran = {4,1};//結構體類型

[mulStr deleteCharactersInRange:ran];

NSLog(@"%@",mulStr);

 

//替換

NSRange ran2 = {3,2};

[mulStr replaceCharactersInRange:ran2 withString:@"yy"];

NSLog(@"%@",mulStr);

 

//插入

[mulStr insertString:@"tt" atIndex:2];

NSLog(@"%@",mulStr);

 

 

// 對於不可變字符串NSString的字符串拼接，分割等操作，都會創建新的字符串

// 對於可變字符串NSMutableString的字符串拼接分割替換等操作是在原字符串的基礎上

// 進行修改，不會創建新字符串

// NSMutableString是NSString的子類，所以NSString的方法，NSMutableString也

//可以使用

// 在以後的學習中，凡是出現Mutable的類，都是不帶Mutable類的子類：

//如,NSMutableArray是NSArray的子類，NSMutableDictionary是NSDictonary的子

//類

==================================================================================== 3.NSArray

 

//數組

//最後的nil不可丟掉

NSArray *arr =[NSArray arrayWithObjects:@"guozai", @"guo",@"zaiguo",nil];

 

// 獲取數組元素個數

NSUInteger count = [arr count];

NSLog(@"%lu",count);

 

 

//獲取第一個對象

NSString *p1 = [arr firstObject];

NSLog(@"%@",p1);

 

 

// 獲取最後一個對象

NSString *p2 = [arr lastObject];

NSLog(@"%@",p2);

 

// 獲取下標對應的對象

NSString *p3 = [arr objectAtIndex:1];

NSLog(@"%@",p3);

 

 

//遍歷數組

for (int i = 0; i < [arr count]; i++) {

NSLog(@"%@",[arr objectAtIndex:i]);

}

===================================================================================== 4.NSMutableArray

 

//可變數組

// 一個數組的內容賦給另一個數組

NSMutableArray * mulArray = [NSMutableArray arrayWithArray:arr];

//刪除下標為index的對象

[mulArray removeObjectAtIndex:2];

 

// for (int i = 0; i < [arr count]; i++) {

// NSLog(@"%@",[arr objectAtIndex:i]);

// }

//

// 添加一個對象元素

[mulArray addObject:@"guoguo"];

 

// 交換下標對應的元素對象

[mulArray exchangeObjectAtIndex:0 withObjectAtIndex:[mulArray count]-1]; //交換第一個元素和最後一個元素

===================================================================================== 下面通過一個實例來形象的了解： 使用可變數組管理BOOk類，實現圖書的增刪查改 BOOK有兩個成員變量：_name,_price;

Book * book1 = [[Book alloc] initWithName:@"guozai1" andPrice:10];

Book * book2 = [[Book alloc] initWithName:@"guozai2" andPrice:15];

Book * book3 = [[Book alloc] initWithName:@"guozai3" andPrice:13];

 

//數組賦值

NSMutableArray *books = [NSMutableArray arrayWithObjects:book1,book2,book3, nil];

 

Book * book4 = [[Book alloc] initWithName:@"guozai4" andPrice:12];

 

//添加一本書

[books addObject:book4];

 

//刪除一本書

[books removeObjectAtIndex:2];

 

for (int i = 0; i < [books count]; i ++) {

NSLog(@"%@,%.2f",[[books objectAtIndex:i] name],[[books objectAtIndex:i] price]);

}

 

 

//查找名字是guozai3的書,打印價格

for (int i = 0; i < [books count]; i ++) {

if ([[[books objectAtIndex:i] name] isEqualToString:@"guozai3"]) {

NSLog(@"%f",[[books objectAtIndex:i] price]);

}

}

 

// 對數組進行排序，按價格從高到低

for (int i = 0; i < [books count] - 1; i ++) {

for (int j = 0; j < [books count] - i - 1; j ++) {

if ([books[j] price] < [books[j+1] price]) {

[books exchangeObjectAtIndex:j withObjectAtIndex:j+1];

}

}

}

 

 

for (int i = 0; i < [books count]; i ++) {

NSLog(@"%@,%.2f",[books[i] name],[books[i] price]);

}

======================================================================================== 5.NSNumber:將基本數據類型轉化成對象類型

//將基本數據類型int轉化為對象類型

NSNumber * intNum = [NSNumber numberWithInt:100];//便利構造器

NSMutableArray * ar = [NSMutableArray arrayWithObjects:intNum, nil];

NSNumber * tem = [ar objectAtIndex:0];

 

//將對象類型轉化成基本數據類型

int result = [tem intValue];

NSLog(@"%d",result);

======================================================================================== 6.NSValue：將結構體轉化成對象

//將一個點轉化成NSValue對象

NSPoint point = {1,2};

//將一個結構體轉化成NSValue對象

NSValue *vPoint = [NSValue valueWithPoint:point];

 

//將vPoint轉化成結構體

NSPoint point2 = [vPoint pointValue];

// NSLog(@"%.2f,%.2f",point2.x,point2.y);

 

// NSStringFromPoint可以將點轉化成字符串

NSLog(@"%@",NSStringFromPoint(point2));

其他的例子類比就行：例如

 

//將NSsize結構體轉化成NSValue對象

NSSize size = {22,44};

NSValue * sValue = [NSValue valueWithSize:size];

 

//將NSValue對象轉化成NSSize結構體；

NSSize size2 = [sValue sizeValue];

NSLog(@"%@", NSStringFromSize(size2));

========================================================================================