iOS design MODE-KVC

Last Update:2016-05-03 Source: Internet

Author: User

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about the design mode of ios, I believe that everyone is not unfamiliar, the most common is the mvc, that is, the Model-view-controller mode, also we often use, this here is not in the narrative, here is the main talk about KVC this mode, if the text has flaws, please the vast number of Bo friends to correct ~ ~ Talk about design PatternsAlthough the design patterns exist in our project projects at all times, we seldom pay attention to them, but use them unconsciously.In the field of software design, The design pattern is a reusable solution to common problems. Design patterns are a series of templates that help you write more understandable and reusable code, and design patterns help you create loosely coupled code so that you can change or replace components in your code without much Effort.So knowing some design patterns helps our code be more prescriptive and clear. Make our code style even Better.Take a deep kvc.KVC full name key valued coding key value codeThe reflection mechanism is in the running state, for any class, can know all the properties and methods of this class, for any one object, can call any of its methods and Properties. Java,c# all have this Mechanism. OBJC also have, so you do not have to do anything at the root of the dynamic read and write properties, that is, kvc.The KVC method is provided by nskeyvaluecoding, which is the NSObject category, which means that almost all objects in OBJC support KVC Operations.Person.h<pre><pre>@interface person:nsobject{ int weight;} @property (nonatomic,readonly, copy) nsstring *name; @property (nonatomic,readonly int *ID id; -(instancetype) initwithdict: (nsdictionary *) dict; @end</pre></pre>Person.m<pre>@implementationperson{int_height;}-(instancetype) initwithdict: (nsdictionary *) dict{if(self=[super Init]) { //common statements for Dictionary-to-model[self setvaluesforkeyswithdictionary:dict]; } returnself ;}//The method that the setting executes when the value of key is undefined- (void) SetValue: (ID) Value Forundefinedkey: (nsstring *) Key {if([key isequaltostring:@"ID"]) {self.id=value; }}//When the value of key is not defined, the method that is executed when the value is taken- (ID) valueforundefinedkey: (nsstring *) Key {if([key isequaltostring:@"ID"]) { returnself.id; } return[NSNullNULL];}</pre>Main.m<pre>Person * P1 =[[person Alloc]init];D og* D1 =[[Dog alloc] init];p 1.dog=d1; //setValue: Attribute value forkey: property name (for simple Path)//when you use KVC to indirectly modify an Object's properties, the system automatically determines the type of the Object's properties and completes the Conversion. such as "170" in the Program. [P1 setValue:@" the"Forkey:@"Height"]; [P1 setValue:@" -"Forkey:@"Weight"]; [P1 setValue:@"1"Forkey:@"ID"];//setValue: Attribute Value forkeypath: Property path (for compound Path)//when using KVC to take a deeply nested path, simply give it a path to take out the desired Attribute. (. can be understood as a path.) has been entered). can help us to code very Convenient. [P1 setValue:@"Dahuan"Forkeypath:@"Dog.name"];//Valueforkey: Property name, valueforkeypath: property name (for compound Path)NSLog (@"height =%d weight =%d ID =%@ dog.name =%@", [[p1 valueforkey:@"Height"] Intvalue],[[p1 valueforkey:@"Weight"] Intvalue],[p1 valueforkey:@"ID"],[P1 Valueforkeypath:@"Dog.name"]); log log: height= theWeight = - ID=11111Dog.name =Dahuan All properties can be assigned successfully nsdictionary* Dict = @{@"Height":@" the", @"Weight":@" -", @"ID":@"11101" }; person* P2 =[[person alloc] initwithdict:dict]; NSLog (@"height =%d weight =%d ID =%@", [[p2 valueforkey:@"Height"] INTVALUE],[[P2 valueforkey:@"Weight"] INTVALUE],[P2 valueforkey:@"ID"]); log log: height= theWeight = - ID=11101All properties can be assigned to a successful value</pre>KVC the order in which attributes are found <ol> <ol> <li>The key value of a property defined with @property</li> <li>The key value of the setter method</li> <li>Direct access to member variables, first find key, if not found, then find _key</li> <li>None of the above three types will be Called-(void) setValue: (id) value forundefinedkey: (nsstring *) key Method.</li> <li>If you do not rewrite the Setvalue:forundefinedkey program will crash immediately.</li> </ol> </ol>Note: KVC can access member variables, regardless of whether the Getter/setter method is provided, whether or not the visibility is readonly Decorated.Application of Setvalue:forundefinedkey and ValueforundefinedkeyThe main use of KVC is not only ORM mapping, is to convert dictionary to model, but some servers return the field may be OC keywords such as ' id ', ' description ' and so On. As the code above the example of the id, we can not let @property after the key value is the id, so use the uppercase ID instead, KVC is case-sensitive we do not worry. In this case, we can avoid the embarrassment of the keyword by assigning the key value of the ID to the key value of the ID in setvalue:forundefinedkey.KVC Bottom-level Implementation<pre><pre>for example, The following line KVC code: [person setValue:@ "Dahuan" forkey:@"name " = Sel_get_uid ("setvalue:forkey:"= Objc_msg_lookup (person-> @"dahuan"@"name");</pre></pre>KVC and runtime applications<pre>#import "MyModel.h"#import<objc/runtime.h>@implementationMyModel//solution file- (ID) Initwithcoder: (nscoder *) decoder{if(self =[super Init]) {unsignedintCount =0; //gets the name of all member variables in the classIvar *ivar = class_copyivarlist ([mymodelclass], &count); for(inti =0; i<count; i++) {Ivar IVA=ivar[i]; Const Char*name =Ivar_getname (iva); NSString*strname =[nsstring stringwithutf8string:name]; //to extract the value of the file IDValue =[decoder decodeobjectforkey:strname]; //using KVC to assign a value to a property[self Setvalue:value forkey:strname]; } Free (ivar); } returnself ;}//Archive- (void) Encodewithcoder: (nscoder *) encoder{unsignedintcount; Ivar*ivar = Class_copyivarlist ([mymodelclass], &count); for(intI=0; i<count; i++) {Ivar IV=ivar[i]; Const Char*name =Ivar_getname (iv); NSString*strname =[nsstring stringwithutf8string:name]; //using KVC to take a value IDValue =[self valueforkey:strname]; [encoder Encodeobject:value forkey:strname]; } Free (ivar);}@end</pre>nsarray/nsset, etc. all support KVC<pre>Person * P1 =[[person Alloc]init];D og* D1 =[[Dog alloc] init];d 1.name=@"IPhone";p 1.dog=d1; person* P2 =[[person Alloc]init];D og* D2 =[[Dog alloc] init];d 2.name=@"iOS";p 2.dog=d2; Nsarray*persons=@[p1,p2]; Nsarray*arraym=[persons Valueforkeypath:@"Dog.name"]; NSLog (@"%@", arraym); log log: (iPhone, IOS)</pre>Reverse use of KVC<pre>Person * P1 =[[person alloc]init]; [P1 setValue:@" the"Forkey:@"Height"]; [P1 setValue:@" -"Forkey:@"Weight"]; [P1 setValue:@"11111"Forkey:@"ID"]; Nsarray* arr = @[@"Height",@"Weight",@"ID"]; Nsdictionary* Dict =[P1 dictionarywithvaluesforkeys:arr]; NSLog (@"%@", dict); log log: {height= the; ID=11111; Weight= -;}</pre>finally, Apple KVC official documents are attached:Https://developer.apple.com/library/mac/documentation/General/Conceptual/DevPedia-CocoaCore/KeyValueCoding.htmliOS design MODE-KVC

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