使用 Objective-C 在 iOS 中的 NSMutableDictionary 中添加值
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Add values in NSMutableDictionary in iOS with Objective-C
提问by Miguel E
I'm starting objective-cdevelopment and I would like to ask the best way to implement a list of keys and values.
我正在开始objective-c开发，我想问一下实现键和值列表的最佳方法。
In Delphi there is the class TDictionaryand I use it like this:
在 Delphi 中有这个类TDictionary，我像这样使用它：
myDictionary : TDictionary<string, Integer>;
bool found = myDictionary.TryGetValue(myWord, currentValue);
if (found)
{
myDictionary.AddOrSetValue(myWord, currentValue+1);
}
else
{
myDictionary.Add(myWord,1);
}
How can I do it in objective-c? Is there equivalent functions to the above mentioned AddOrSetValue() or TryGetValue()?
我怎样才能做到objective-c？是否有与上述等效的功能AddOrSetValue() or TryGetValue()？
Thank you.
谢谢你。
回答by Tom Jefferys
You'd want to implement your example along these lines:
您希望按照以下方式实现您的示例：
EDIT:
编辑：
//NSMutableDictionary myDictionary = [[NSMutableDictionary alloc] init];
NSMutableDictionary *myDictionary = [[NSMutableDictionary alloc] init];
NSNumber *value = [myDictionary objectForKey:myWord];
if (value)
{
NSNumber *nextValue = [NSNumber numberWithInt:[value intValue] + 1];
[myDictionary setObject:nextValue forKey:myWord];
}
else
{
[myDictionary setObject:[NSNumber numberWithInt:1] forKey:myWord]
}
(Note: you can't store ints or other primitives directly in a NSMutableDictionary, hence the need to wrap them in an NSNumberobject, and make sure you call [myDictionary release]when you've finished with the dictionary).
（注意：您不能将整数或其他原语直接存储在 a 中NSMutableDictionary，因此需要将它们包装在一个NSNumber对象中，并确保[myDictionary release]在完成字典后调用）。
回答by Jesse Rusak
The other answers are correct, but there is more modern syntax for this now. Rather than:
其他答案是正确的，但现在有更现代的语法。而不是：
[myDictionary setObject:nextValue forKey:myWord];
You can simply say:
你可以简单地说：
myDictionary[myWord] = nextValue;
Similarly, to get a value, you can use myDictionary[key]to get the value (or nil).
同样，要获取一个值，您可以使用myDictionary[key]来获取该值（或 nil）。
回答by Williham Totland
Yep:
是的：
- (id)objectForKey:(id)key;
- (void)setObject:(id)object forKey:(id)key;
setObject:forKey:overwrites any existing object with the same key; objectForKey:returns nilif the object doesn't exist.
setObject:forKey:用相同的键覆盖任何现有对象；如果对象不存在则objectForKey:返回nil。
Edit:
编辑：
Example:
例子：
- (void)doStuff {
NSMutableDictionary *dict = [NSMutableDictionary dictionary];
[dict setObject:@"Foo" forKey:@"Key_1"]; // adds @"Foo"
[dict setObject:@"Bar" forKey:@"Key_2"]; // adds @"Bar"
[dict setObject:@"Qux" forKey:@"Key_2"]; // overwrites @"Bar"!
NSString *aString = [dict objectForKey:@"Key_1"]; // @"Foo"
NSString *anotherString = [dict objectForKey:@"Key_2"]; // @"Qux"
NSString *yas = [dict objectForKey:@"Key_3"]; // nil
}
Reedit:For the specific example there exists a more compact approach:
Reedit：对于特定示例，存在更紧凑的方法：
[dict
setObject:
[NSNumber numberWithInteger:([[dict objectForKey:@"key"] integerValue] + 1)]
forKey:
@"key"
];
Crazy indentation for readability.
疯狂的缩进以提高可读性。
