Object-C 基础学习（二）

7.if条件语句

for example:

BOOL mrHiggieIsMean = YES;//BOOL类型值，以YES和NO来区分

if (mrHiggieIsMean) {
NSLog(@"Confirmed: he is super mean");
}

if-else if-else语法

8.switch(expression){

case value:

break;
}

与其他编程语言语法一样

9.for循环

for example:

NSArray *newHats = @[@"Cowboy", @"Conductor", @"Baseball"];

for (NSString *hat in newHats) {

NSLog(@"Trying on new %@ hat", hat);

if([mrHiggie tryOnHat:hat]) {
NSLog(@"Mr. Higgie loves it");
} else {
NSLog(@"Mr. Higgie hates it");
}
}

针对于NSDictionary(键值对)：

NSDictionary *funnyWords = @{
  @"Schadenfreude": @"pleasure derived by someone from another person's misfortune.",
  @"Portmanteau": @"consisting of or combining two or more separable aspects or qualities",
  @"Penultimate": @"second to the last"
};

for (NSString *word in funnyWords) {
  NSString *definition = funnyWords[word];
  NSLog(@"%@ is defined as %@", word, definition);
}

 10.block 代码块，类似于object，只不过前边不用“*”，而是用“^”；

for example:

（一）Blocks with no arguments:

void (^logMessage)(void) = ^{//第一个void为返回类型，第二个void为argument参数类型。
  NSLog(@"Hello from inside the block");
};
logMessage();//调用block（代码块）

(二)Blocks with arguments:

基本类型：

void (^sumNumbers)(NSUInteger, NSUInteger) = ^(NSUInteger num1, NSUInteger num2){
  NSLog(@"The sum of the numbers is %lu", num1 + num2);
};

sumNumbers(45, 89);
sumNumbers(18, 56);、

对象类型：

NSArray和NSString类型

void (^logCount)(NSArray *) = ^(NSArray *array){
  NSLog(@"There are %lu objects in this array", [array count]);
};

logCount(@[@"Mr.", @"Higgie"]);
logCount(@[@"Mr.", @"Jony", @"Ive", @"Higgie"]);

void (^myFirstBlock)(NSString *) = ^(NSString *string){
  NSLog(@"Hello from inside the block include %@",string);
};

myFirstBlock(@"Hello");
myFirstBlock(@"World");