Common options < Data source protocols, delegation agreements > (iOS development)

-The common choice must be fulfilled by the two protocols that are agreed to implement. One for the data source protocol

-the Trust agreement is responsible for controlling the UIof the control, event response , and implementing optional

-The data source protocol is responsible for the bridge between the control and the application data model, generally must implement

@interface Viewcontroller:uiviewcontroller <uipickerviewdelegate, uipickerviewdatasource>

  viewcontroller.h//  pickviewsample////  Created by Li Yakun on 14-10-21.//  Copyright (c) 2014 Li Yakun. All rights reserved.//#import <UIKit/UIKit.h> @interface viewcontroller:uiviewcontroller< Uipickerviewdelegate, uipickerviewdatasource>//Ordinary selectors must satisfy both protocols, one for the trust agreement, one for the data source Protocol//Trust protocol to control the control UI, the event response, to implement optional// The data source protocol is responsible for the bridge between the control and the application data model, generally must implement @property (weak, nonatomic) Iboutlet Uipickerview *pickerview; @property (weak, nonatomic) Iboutlet UILabel *label; @property (nonatomic, strong) nsdictionary *pickerdata;     Save All data @property (nonatomic, strong) Nsarray *pickerprovincesdata; Current provincial data @property (Nonatomic, strong) Nsarray *pickercitiesdata;    City data below current province-(ibaction) onclick: (id) sender; @end

viewcontroller.m//pickviewsample////Created by Li Yakun on 14-10-21.//Copyright (c) 2014 Li Yakun. All rights reserved.//#import "ViewController.h" @interface Viewcontroller () @end @implementation viewcontroller-(void    ) Viewdidload {[Super viewdidload];        Additional setup after loading the view, typically from a nib.    Locate the folder to specify the file and return the file path nsbundle *bundle = [NSBundle mainbundle]; NSString *plistpath = [Bundle pathforresource:@ "Provinces_cities" oftype:@ "plist        "];    Get all the data in the attribute list file nsdictionary *dict = [[Nsdictionary alloc] initwithcontentsoffile:plistpath];        Self.pickerdata = Dict;        Province name self.pickerprovincesdata = [Self.pickerdata AllKeys];    The default is to take out the data for all municipalities in the first province nsstring *seletedprovince = [Self.pickerprovincesdata objectatindex:0];   Objectforkey: Find the data of the index self.pickercitiesdata = [Self.pickerdata objectforkey:seletedprovince];  

 Self.pickView.data Source = self; 

    Self.pickView.delegate = self;}    -(void) didreceivememorywarning {[Super didreceivememorywarning]; Dispose of any resources the can be recreated.}    -(Ibaction) onclick: (ID) Sender {//Set the selected row index starting from 0 nsinteger row1 = [Self.pickerview selectedrowincomponent:0];    Nsinteger row2 = [Self.pickerview selectedrowincomponent:1];    NSString *selected1 = [Self.pickerprovincesdata Objectatindex:row1];        NSString *selected2 = [Self.pickercitiesdata objectatindex:row2];    NSString *title = [[NSString alloc] initwithformat:@ "%@,%@ City", Selected1, Selected2]; Self.label.text = title;} #pragma mark Implementation Protocol Uipickerviewdatasource Method-(Nsinteger) Numberofcomponentsinpickerview: (Uipickerview *) pickerview{// Returns the number of dials in the selector return 2;}  -(Nsinteger) Pickerview: (Uipickerview *) Pickerview numberofrowsincomponent: (nsinteger) component{//Returns the number of rows in a selected dial if (component = = 0)    {//Returns the number of provinces return [Self.pickerprovincesdata Count]; } else {//returns the number of cities return [Self.pickercitiesdata Count]; }} #pragma mark implements the protocol Uipickerviewdelegate method//provides display data for a row of a dial in the selector-(NSString *) Pickerview: (Uipickerview *) Pickerview Titleforrow: (Nsinteger) Row forcomponent: (Nsinteger) component{if (component = = 0) {//Select the province's name return [self    . Pickerprovincesdata Objectatindex:row];    } else {return [self.pickercitiesdata Objectatindex:row]; }}//when a row in a dial is selected, call-(void) Pickerview: (Uipickerview *) Pickerview Didselectrow: (nsinteger) Row incomponent: (Nsinteger        ) component{if (component = = 0) {nsstring *seletedprovince = [Self.pickerprovincesdata objectatindex:row];        Nsarray *array = [Self.pickerdata objectforkey:seletedprovince];        Self.pickercitiesdata = array;    Refresh [Self.pickerview reloadcomponent:1]; }} @end

The implementation object of the entrusted and the data source Viewcontroller assigned to the Uipickerview attribute delegate and the data source attribute datasource;

This part can be implemented in Interfacebuilder. The assignment will generate itself voluntarily

-(void) viewdidload

{

...

Self.pickerView.dataSource = self;

Self.pickerView.delegate = self;

}

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Common options &lt; Data source protocols, delegation agreements &gt; (iOS development)