IOS [switch]setvalue and SetObject differences

<span id="Label3"></p><p><p>SetValue Forkey and SetObject forkey are often used when using nsmutabledictionary, and they can often be used interactively, often in every use of the Code.</p></p><p><p>1, First look at the definition of setvalue:forkey:</p></p><p><p></p></p><p><p>@interface Nsmutabledictionary (nskeyvaluecoding)</p></p><p><p>/* send-setobject:forkey:to the receiver, unless the value is nil, in which case send-removeobject:forkey:.</p></p><p><p>*/</p></p><p><p>-(void) setValue: (id) value forkey: (nsstring *) key;</p></p><p><p>@end</p></p><p><p>Extension Nsmutabledictionary A category, the above comment is very clear, send Setobject:forkey to the receiver, that is, call Setobject:forkey method</p></p><p><p>Unless value is nil, the method is called Removeobject:forkey</p></p><p><p></p></p><p><p>2, look at the definition of setobject:forkey:</p></p><p><p></p></p><p><p>@interface Nsmutabledictionary:nsdictionary</p></p><p><p>-(void) removeobjectforkey: (id) akey;</p></p><p><p>-(void) setobject: (id) anobject forkey: (id <NSCopying>) akey;</p></p><p><p>@end</p></p><p><p><span style="color: #ff0000;">Note: setobject:forkey: The object in key is an ID type, not a nsstring, but we often use nsstring.</span></p></p><p><p></p></p><p><p>Now the difference between the 2 of them is:</p></p><p><p>1, setobject:forkey: in value is not able to nil, or will Error.</p></p><p><p>Setvalue:forkey: value can be nil, but when value is nil, the Removeobject:forkey method is called automatically</p></p><p><p>2, setvalue:forkey: The parameter in key can only be nsstring type, and setobject:forkey: can be any type</p></p><p><p></p></p><p><p><span style="color: #ff0000;">Note: Setobject:forkey: objects cannot hold nil to differentiate from this situation:</span></p></p><p><p></p></p><p><p><span style="color: #ff0000;">1, [imagedictionarysetobject:[nsnullnull] forkey:indexnumber];</span></p></p><p><p><span style="color: #ff0000;">[NSNull null] represents an empty object, not nil, Note this</span></p></p><span style="color: #ff0000;"><span style="color: #ff0000;"> </span></span><p><p><span style="color: #ff0000;"></span></p></p><p><p><span style="color: #ff0000;">2, setobject:forkey: When key is the NSNumber object, the Following:</span></p></p><p><p><span style="color: #ff0000;">[imagedictionarysetobject:obj Forkey:[nsnumber numberwithint:10];</span></p></p><p><p></p></p><p><p><span style="color: #ff0000;">Attention:</span></p></p><p><p><span style="color: #ff0000;">The difference mentioned above is for the caller to be dictionary.</span></p></p><p><p><span style="color: #ff0000;">Setobject:forkey: method Nsmutabledictionary peculiar, and</span></p></p><p><p><span style="color: #ff0000;">Setvalue:forkey: method is the main method of KVC (key-value encoding).</span></p></p><p><p><span style="color: #ff0000;"></span></p></p><p><p><span style="color: #888888;">When setvalue:forkey: the method caller is an object:</span></p></p><p><p><span style="color: #888888;">Setvalue:forkey: The method is created in the NSObject object, which means that all OC objects have this method, so they can be used in any class.</span></p></p><p><p><span style="color: #888888;">For example, use:</span></p></p><p><p><span style="color: #888888;">SomeClass *someobj = [[someclass alloc] init];</span></p></p><p><p><span style="color: #888888;">[someobj setvalue:self forkey:@ "delegate"];</span></p></p><p><p><span style="color: #888888;">Object Someobj Set the value of his delegate property to the current class, and of course the object calling this method must have a delegate property to set, or the call will not be effective</span></p></p><p><p><span style="color: #ff0000;"></span></p></p><p><p>IOS [switch]setvalue and SetObject differences</p></p></span>