objective-c 在目标 c 中切换 NSString 的大小写
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switch case on NSString in objective c
提问by nmokkary
i want to use case statement with NSString please change my code to correct code
我想在 NSString 中使用 case 语句，请将我的代码更改为正确的代码
NSString *day = @"Wed";
switch (day) {
case @"Sat":
NSlog(@"Somthing...");
break;
case @"Sun":
NSlog(@"Somthing else...");
break;
.
.
.
.
default:
break;
}
回答by Nikolai Ruhe
If you want some slightly smarter dispatch than a long list of conditionals you can use a dictionary of blocks:
如果你想要一些比一长串条件更智能的调度，你可以使用块字典：
NSString *key = @"foo";
void (^selectedCase)() = @{
@"foo" : ^{
NSLog(@"foo");
},
@"bar" : ^{
NSLog(@"bar");
},
@"baz" : ^{
NSLog(@"baz");
},
}[key];
if (selectedCase != nil)
selectedCase();
If you have a really long list of cases and you do this often, there might be a tiny performance advantage in this. You should cache the dictionary, then (and don't forget to copy the blocks).
如果您有很长的案例列表并且经常这样做，那么这可能会带来很小的性能优势。然后你应该缓存字典（不要忘记复制块）。
Sacrificing legibility for convenience and brevity here's a version that fits everything into a single statement and adds a default case:
为了方便和简洁而牺牲了易读性，这是一个将所有内容放入单个语句并添加默认情况的版本：
((void (^)())@{
@"foo" : ^{
NSLog(@"foo");
},
@"bar" : ^{
NSLog(@"bar");
},
@"baz" : ^{
NSLog(@"baz");
},
}[key] ?: ^{
NSLog(@"default");
})();
I prefer the former.
我更喜欢前者。
回答by Antonio MG
Switchstatements don′t work with NSString, only with integers. Use if else:
Switch语句不适用于 NSString，只能用于整数。使用if else：
NSString *day = @"Wed";
if([day isEqualToString:@"Sat"]) {
NSlog(@"Somthing...");
}
else if([day isEqualToString:@"Sun"]) {
NSlog(@"Somthing...");
}
...
