xcode 来自 NSArray 的 NSString
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NSString from NSArray
提问by NNikN
I am trying to create a String from Array.But, there is condition to how it should be generated, as explained below.
我正在尝试从 Array 创建一个字符串。但是，如何生成它是有条件的，如下所述。
NSArray *array=[NSArray arrayWithObjects:@"Hello",@"World",nil];
[array componentsJoinedByString:@","];
This will output: Hello,World.
这将输出：你好，世界。
But, if first Item is Empty,then is there way to receive the only second one.
但是，如果第一个项目是空的，那么有没有办法接收唯一的第二个项目。
- Hello , @"" => Hello
- @"" , World => World
- Hello , World => Hello,World
- 你好，@"" => 你好
- @"" , 世界 => 世界
- 你好，世界 => 你好，世界
回答by Alladinian
Another way to do this is to grab a mutable copy of the array and just remove non valid objects. Something like this perhaps:
另一种方法是获取数组的可变副本并删除无效对象。可能是这样的：
NSMutableArray *array = [[NSArray arrayWithObjects:@"",@"World",nil] mutableCopy];
[array removeObject:@""]; // Remove empty strings
[array removeObject:[NSNull null]]; // Or nulls maybe
NSLog(@"%@", [array componentsJoinedByString:@","]);
回答by dasblinkenlight
You cannot store nilvalues in NSArray*, so the answer is "no". You need to iterate the array yourself, keeping track of whether you need to add a comma or not.
您不能将nil值存储在NSArray* 中，因此答案是否定的。您需要自己迭代数组，跟踪是否需要添加逗号。
NSMutableString *res = [NSMutableString string];
BOOL first = YES;
for(id item in array) {
if (id == [NSNull null]) continue;
// You can optionally check for item to be an empty string here
if (!first) {
[res appendString:@", "];
} else {
first = NO;
}
[res appendFormat:@"%@", item];
}
**
nilnilNS 集合中的值用NSNullNSNull对象表示。