在Objective-C 中使用字符生成NSArray、NSDictionary、NSNumber

@符号不仅可以生成字符串，还可以生成其他数据类型如NSArray、NSDictionary和NSNumber，是一种简洁快速的用法。

// NSArray
array = [NSArray arrayWithObjects:a, b, c, nil];

array = @[ a, b, c ];

// NSDictionary
dict = [NSDictionary dictionaryWithObjects:@[o1, o2, o3] forKeys:@[k1, k2, k3]];

dict = @{ k1 : o1, k2 : o2, k3 : o3 };

// NSNumber
NSNumber *number;
number = [NSNumber numberWithChar:'X'];
number = [NSNumber numberWithInt:12345];
number = [NSNumber numberWithUnsignedLong:12345ul];
number = [NSNumber numberWithLongLong:12345ll];
number = [NSNumber numberWithFloat:123.45f];
number = [NSNumber numberWithDouble:123.45];
number = [NSNumber numberWithBool:YES];

NSNumber *number;
number = @'X';
number = @12345;
number = @12345ul;
number = @12345ll;
number = @123.45f;
number = @123.45;
number = @YES;

　http://boboshone.com/blog/2013/04/20/objective-c-literals-nsarray-nsdictionary-nsnumber/