Object-C 基础学习（一）

1.数组

NSArray *arrays = @[@"keyname",@"value"];

 

2.输出

NSArray *array = [arrays,description];

NSLog(@"print Array %@",array);

%@是占位符，针对于NSUInteger，如果输出得采用%lu来代替

for example:

NSString *city = @"Ice World";
NSUInteger cityLength = [city length];

NSLog(@"City has %lu characters", cityLength);

 

3.NSNumber

NSNumber *higgiesAge = @6;
NSNumber *phoneLives = @3;

对比其他变成语言，想要获得他们的乘积，直接NSNumber *result = higgiesAge * phoneLives;即可，但对于Object-C来说，这样做不正确，要先转换成NSUInteger类型才可以。

for example:

NSUInteger higgiesAgeInt = [higgiesAge unsignedIntegerValue];//将higgiesAge转换成NSUInteger类型
NSUInteger phoneLivesInt = [phoneLives unsignedIntegerValue];//将phoneLives转换成NSUInteger类型
NSUInteger higgiesRealAge = higgiesAgeInt * phoneLivesInt;//计算乘积
NSLog(@"final result is %lu :",higgiesRealAge );//输出NSUInteger类型的数据

4.字符串拼接

NSString *firstName = @"Hello,Mr.Higgie";
NSString *lastName =@"Jack-Lu";

NSString *fullName = [firstName stringByAppendingString:lastName];//通过一个特定的方法

//NSString *fullName = [ [firstName stringByAppendingString:@" "] stringByAppendingString:lastName];//两个字符串之间以空格分开，类似于SQL语句中的子查询

//另一种方式更加简单：NSString * fullName = [NSString stringWithFormat:@"%@  %@",firstName,lastName];
NSLog(@"%@", fullName);

5.class对象

NSString 也是一个class，创建一个NSString并赋值。

for example：

NSString *firstName = @"Hello,Mr.Higgie";

NSString *copy = [NSString stringWithString:@"Jack"];

NSLog(@"%@ is a copy of %@", copy, firstName);

6.Create an empty object:

创建一个空数组：

NSArray *emptyArray = [NSArray array];

创建一个空dictionary：

NSDictionary *emptyDict = [NSDictionary dictionary];

换一种方式创建empty object：

NSString *emptyString = [[NSString alloc] init];
NSArray *emptyArray = [[NSArray alloc] init];
NSDictionary *emptyDictionary = [[NSDictionary alloc] init];

但是初始化一个空的object往往是没有意义的，因此，初始化一个带数据的object：

NSString *copy = [[NSString alloc] initWithString:otherString];

for example:

NSString * firstName = @"Hello,Mr.Higgie";
NSString * copy = [[NSString alloc] initWithString:@"Jack-Lu"];
NSLog(@"%@ is a copy of %@",copy,firstName);