场景
- 在开发
Cocoa
程序时,由于界面是用Objective-C
写的。无法使用C++
的目标观察者[1]类。如果是使用第二种方案2[2],那么也需要增加一个代理类。那么有没有更省事的办法?
说明
-
开发界面的时候,经常是需要在子界面里传递数据给主界面,主界面获得数据后跟业务逻辑交互。目前子界面和主界面的数据交互目前使用发布订阅(观察者模式)的设计模式是比较好的,因为它可以让两个界面解耦合。
-
之前说过在
Cocoa
程序里,可以使用NSNotificationCenter通知中心发布接收消息注意事项来作为消息传递的观察者实现。这里要强调一个问题,就是NSNotificationCenter
注册的观察者必须要设置接收对象,也就是以下的object
参数。如果参数设置为nil
,当有多个地方注册同样的观察者时,目标如果发送MyNotificationChangeBackgroundColor
消息,所有的观察者都有接收到这个消息,会导致该消息执行多次。特别是以下代码self
对象是多个实例时。
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(recvNotificationMessage:) name:@(MyNotificationChangeBackgroundColor) object:subject];
- 发送
MyNotificationChangeBackgroundColor
消息, 注意要指定object
参数值。
-(IBAction)onChange:(id)sender
{static int mod = 1;if(mod++ % 2){NSColor* color = [NSColor colorWithSRGBRed:255/255.0 green:255/255.0 blue:255/255.0 alpha:1];[[NSNotificationCenter defaultCenter] postNotificationName:@(MyNotificationChangeBackgroundColor) object:self userInfo:@{@"color":color}];}else{NSColor* color = [NSColor colorWithSRGBRed:240/255.0 green:122/255.0 blue:55/255.0 alpha:1];[[NSNotificationCenter defaultCenter] postNotificationName:@(MyNotificationChangeBackgroundColor) object:view1_ userInfo:@{@"color":color}];}}
例子
- 以下例子说明如何创建响应指定目标的观察者。点击两次
Change
按钮会依次更改子视图1
和2
的背景色,而它们发送的是同样的消息。
AppDelegate.h
#import <Cocoa/Cocoa.h>
#import "MyView.h"@interface AppDelegate : NSObject <NSApplicationDelegate>
{IBOutlet MyView* view1_;IBOutlet MyView* view2_;
}-(IBAction)onChange:(id)sender;-(IBAction)onReset:(id)sender;@end
AppDelegate.mm
#import "AppDelegate.h"
#include "platform.h"@interface AppDelegate ()@property (weak) IBOutlet NSWindow *window;
@end@implementation AppDelegate-(void)changeBackgroundColor:(NSView*)view withColor:(NSColor*)color1
{[view setWantsLayer:YES];CGColorSpaceRef space = [[color1 colorSpace] CGColorSpace];CGFloat components[] ={color1.redComponent,color1.greenComponent,color1.blueComponent,color1.alphaComponent};CGColorRef color_ref = CGColorCreate(space,components);[[view layer] setBackgroundColor:color_ref];CGColorRelease(color_ref);
}- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {// Insert code here to initialize your application[self onReset:nil];[view1_ registerObserver:self]; // 只接收来自self的消息[view2_ registerObserver:view1_]; // 只接收来自view1的消息
}- (void)applicationWillTerminate:(NSNotification *)aNotification {// Insert code here to tear down your application
}-(IBAction)onChange:(id)sender
{static int mod = 1;if(mod++ % 2){NSColor* color = [NSColor colorWithSRGBRed:255/255.0 green:255/255.0 blue:255/255.0 alpha:1];[[NSNotificationCenter defaultCenter] postNotificationName:@(MyNotificationChangeBackgroundColor) object:self userInfo:@{@"color":color}];}else{NSColor* color = [NSColor colorWithSRGBRed:240/255.0 green:122/255.0 blue:55/255.0 alpha:1];[[NSNotificationCenter defaultCenter] postNotificationName:@(MyNotificationChangeBackgroundColor) object:view1_ userInfo:@{@"color":color}];}}-(IBAction)onReset:(id)sender
{[self changeBackgroundColor:view1_ withColor:[NSColor redColor]];[self changeBackgroundColor:view2_ withColor:[NSColor blueColor]];
}@end
MyView.h
#import <Cocoa/Cocoa.h>NS_ASSUME_NONNULL_BEGIN@interface MyView : NSView-(void)registerObserver:(id __nullable)subject;-(void)removeObserver:(id)subject;@endNS_ASSUME_NONNULL_END
MyView.mm
#import "MyView.h"
#include "platform.h"@implementation MyView- (void)drawRect:(NSRect)dirtyRect {[super drawRect:dirtyRect];// Drawing code here.
}-(void)changeBackgroundColor:(NSView*)view withColor:(NSColor*)color1
{[view setWantsLayer:YES];CGColorSpaceRef space = [[color1 colorSpace] CGColorSpace];CGFloat components[] ={color1.redComponent,color1.greenComponent,color1.blueComponent,color1.alphaComponent};CGColorRef color_ref = CGColorCreate(space,components);[[view layer] setBackgroundColor:color_ref];CGColorRelease(color_ref);
}-(void)recvNotificationMessage:(NSNotification*) notification
{if([notification.name compare:@(MyNotificationChangeBackgroundColor)] == NSOrderedSame){NSDictionary* dict = notification.userInfo;NSColor* color = [dict objectForKey:@"color"];[self changeBackgroundColor:self withColor:color];}
}-(void)registerObserver:(id)subject
{[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(recvNotificationMessage:) name:@(MyNotificationChangeBackgroundColor) object:subject];
}-(void)removeObserver:(id)subject
{[[NSNotificationCenter defaultCenter] removeObserver:self name:@(MyNotificationChangeBackgroundColor) object:subject];
}-(void)awakeFromNib
{}@end
platform.h
#ifndef platform_h
#define platform_h#define MyNotificationChangeBackgroundColor "MyNotificationChangeBackgroundColor"#endif /* platform_h */
main.m
#import <Cocoa/Cocoa.h>int main(int argc, const char * argv[]) {return NSApplicationMain(argc, argv);
}
MainMenu.xib
<?xml version="1.0" encoding="UTF-8"?>
<document type="com.apple.InterfaceBuilder3.Cocoa.XIB" version="3.0" toolsVersion="14460.31" targetRuntime="MacOSX.Cocoa" propertyAccessControl="none" useAutolayout="YES" customObjectInstantitationMethod="direct"><dependencies><plugIn identifier="com.apple.InterfaceBuilder.CocoaPlugin" version="14460.31"/><capability name="documents saved in the Xcode 8 format" minToolsVersion="8.0"/></dependencies><objects><customObject id="-2" userLabel="File's Owner" customClass="NSApplication"><connections><outlet property="delegate" destination="Voe-Tx-rLC" id="GzC-gU-4Uq"/></connections></customObject><customObject id="-1" userLabel="First Responder" customClass="FirstResponder"/><customObject id="-3" userLabel="Application"/><customObject id="Voe-Tx-rLC" customClass="AppDelegate"><connections><outlet property="view1_" destination="Gxg-KB-hXo" id="0fI-03-3v8"/><outlet property="view2_" destination="4YQ-ZK-Q0W" id="4bZ-O9-7Dg"/><outlet property="window" destination="QvC-M9-y7g" id="gIp-Ho-8D9"/></connections></customObject><customObject id="YLy-65-1bz" customClass="NSFontManager"/><menu title="Main Menu" systemMenu="main" id="AYu-sK-qS6"><items><menuItem title="NotificationTest" id="1Xt-HY-uBw"><modifierMask key="keyEquivalentModifierMask"/><menu key="submenu" title="NotificationTest" systemMenu="apple" id="uQy-DD-JDr"><items><menuItem title="About NotificationTest" id="5kV-Vb-QxS"><modifierMask key="keyEquivalentModifierMask"/><connections><action selector="orderFrontStandardAboutPanel:" target="-1" id="Exp-CZ-Vem"/></connections></menuItem><menuItem isSeparatorItem="YES" id="VOq-y0-SEH"/><menuItem title="Preferences…" keyEquivalent="," id="BOF-NM-1cW"/><menuItem isSeparatorItem="YES" id="wFC-TO-SCJ"/><menuItem title="Services" id="NMo-om-nkz"><modifierMask key="keyEquivalentModifierMask"/><menu key="submenu" title="Services" systemMenu="services" id="hz9-B4-Xy5"/></menuItem><menuItem isSeparatorItem="YES" id="4je-JR-u6R"/><menuItem title="Hide NotificationTest" keyEquivalent="h" id="Olw-nP-bQN"><connections><action selector="hide:" target="-1" id="PnN-Uc-m68"/></connections></menuItem><menuItem title="Hide Others" keyEquivalent="h" id="Vdr-fp-XzO"><modifierMask key="keyEquivalentModifierMask" option="YES" command="YES"/><connections><action selector="hideOtherApplications:" target="-1" id="VT4-aY-XCT"/></connections></menuItem><menuItem title="Show All" id="Kd2-mp-pUS"><modifierMask key="keyEquivalentModifierMask"/><connections><action selector="unhideAllApplications:" target="-1" id="Dhg-Le-xox"/></connections></menuItem><menuItem isSeparatorItem="YES" id="kCx-OE-vgT"/><menuItem title="Quit NotificationTest" keyEquivalent="q" id="4sb-4s-VLi"><connections><action selector="terminate:" target="-1" id="Te7-pn-YzF"/></connections></menuItem></items></menu></menuItem><menuItem title="File" id="dMs-cI-mzQ"><modifierMask key="keyEquivalentModifierMask"/><menu key="submenu" title="File" id="bib-Uj-vzu"><items><menuItem title="New" keyEquivalent="n" id="Was-JA-tGl"><connections><action selector="newDocument:" target="-1" id="4Si-XN-c54"/></connections></menuItem><menuItem title="Open…" keyEquivalent="o" id="IAo-SY-fd9"><connections><action selector="openDocument:" target="-1" id="bVn-NM-KNZ"/></connections></menuItem><menuItem title="Open Recent" id="tXI-mr-wws"><modifierMask key="keyEquivalentModifierMask"/><menu key="submenu" title="Open Recent" systemMenu="recentDocuments" id="oas-Oc-fiZ"><items><menuItem title="Clear Menu" id="vNY-rz-j42"><modifierMask key="keyEquivalentModifierMask"/><connections><action selector="clearRecentDocuments:" target="-1" id="Daa-9d-B3U"/></connections></menuItem></items></menu></menuItem><menuItem isSeparatorItem="YES" id="m54-Is-iLE"/><menuItem title="Close" keyEquivalent="w" id="DVo-aG-piG"><connections><action selector="performClose:" target="-1" id="HmO-Ls-i7Q"/></connections></menuItem><menuItem title="Save…" keyEquivalent="s" id="pxx-59-PXV"><connections><action selector="saveDocument:" target="-1" id="teZ-XB-qJY"/></connections></menuItem><menuItem title="Save As…" keyEquivalent="S" id="Bw7-FT-i3A"><connections><action selector="saveDocumentAs:" target="-1" id="mDf-zr-I0C"/></connections></menuItem><menuItem title="Revert to Saved" keyEquivalent="r" id="KaW-ft-85H"><connections><action selector="revertDocumentToSaved:" target="-1" id="iJ3-Pv-kwq"/></connections></menuItem><menuItem isSeparatorItem="YES" id="aJh-i4-bef"/><menuItem title="Page Setup…" keyEquivalent="P" id="qIS-W8-SiK"><modifierMask key="keyEquivalentModifierMask" shift="YES" command="YES"/><connections><action selector="runPageLayout:" target="-1" id="Din-rz-gC5"/></connections></menuItem><menuItem title="Print…" keyEquivalent="p" id="aTl-1u-JFS"><connections><action selector="print:" target="-1" id="qaZ-4w-aoO"/></connections></menuItem></items></menu></menuItem><menuItem title="Edit" id="5QF-Oa-p0T"><modifierMask key="keyEquivalentModifierMask"/><menu key="submenu" title="Edit" id="W48-6f-4Dl"><items><menuItem title="Undo" keyEquivalent="z" id="dRJ-4n-Yzg"><connections><action selector="undo:" target="-1" id="M6e-cu-g7V"/></connections></menuItem><menuItem title="Redo" keyEquivalent="Z" id="6dh-zS-Vam"><connections><action selector="redo:" target="-1" id="oIA-Rs-6OD"/></connections></menuItem><menuItem isSeparatorItem="YES" id="WRV-NI-Exz"/><menuItem title="Cut" keyEquivalent="x" id="uRl-iY-unG"><connections><action selector="cut:" target="-1" id="YJe-68-I9s"/></connections></menuItem><menuItem title="Copy" keyEquivalent="c" id="x3v-GG-iWU"><connections><action selector="copy:" target="-1" id="G1f-GL-Joy"/></connections></menuItem><menuItem title="Paste" keyEquivalent="v" id="gVA-U4-sdL"><connections><action selector="paste:" target="-1" id="UvS-8e-Qdg"/></connections></menuItem><menuItem title="Paste and Match Style" keyEquivalent="V" id="WeT-3V-zwk"><modifierMask key="keyEquivalentModifierMask" option="YES" command="YES"/><connections><action selector="pasteAsPlainText:" target="-1" id="cEh-KX-wJQ"/></connections></menuItem><menuItem title="Delete" id="pa3-QI-u2k"><modifierMask key="keyEquivalentModifierMask"/><connections><action selector="delete:" target="-1" id="0Mk-Ml-PaM"/></connections></menuItem><menuItem title="Select All" keyEquivalent="a" id="Ruw-6m-B2m"><connections><action selector="selectAll:" target="-1" id="VNm-Mi-diN"/></connections></menuItem><menuItem isSeparatorItem="YES" id="uyl-h8-XO2"/><menuItem title="Find" id="4EN-yA-p0u"><modifierMask key="keyEquivalentModifierMask"/><menu key="submenu" title="Find" id="1b7-l0-nxx"><items><menuItem title="Find…" tag="1" keyEquivalent="f" id="Xz5-n4-O0W"><connections><action selector="performFindPanelAction:" target="-1" id="cD7-Qs-BN4"/></connections></menuItem><menuItem title="Find and Replace…" tag="12" keyEquivalent="f" id="YEy-JH-Tfz"><modifierMask key="keyEquivalentModifierMask" option="YES" command="YES"/><connections><action selector="performFindPanelAction:" 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title="Subscript" id="I0S-gh-46l"><modifierMask key="keyEquivalentModifierMask"/><connections><action selector="subscript:" target="-1" id="Q6W-4W-IGz"/></connections></menuItem><menuItem title="Raise" id="2h7-ER-AoG"><modifierMask key="keyEquivalentModifierMask"/><connections><action selector="raiseBaseline:" target="-1" id="4sk-31-7Q9"/></connections></menuItem><menuItem title="Lower" id="1tx-W0-xDw"><modifierMask key="keyEquivalentModifierMask"/><connections><action selector="lowerBaseline:" target="-1" id="OF1-bc-KW4"/></connections></menuItem></items></menu></menuItem><menuItem isSeparatorItem="YES" id="Ndw-q3-faq"/><menuItem title="Show Colors" keyEquivalent="C" id="bgn-CT-cEk"><connections><action selector="orderFrontColorPanel:" target="-1" id="mSX-Xz-DV3"/></connections></menuItem><menuItem isSeparatorItem="YES" id="iMs-zA-UFJ"/><menuItem title="Copy Style" keyEquivalent="c" id="5Vv-lz-BsD"><modifierMask key="keyEquivalentModifierMask" option="YES" 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</document>
例子
图1
参考
1.观察者模式在项目中实际使用例子
2.观察者模式在项目中实际使用例子2
3.NSNotificationCenter通知中心发布接收消息注意事项