SwiftUI

Charts are not present in every mobile app, but they are quite common in sports, health, and finance applications. In this post, we’ll learn how to:

• Create a chart (bar and line)
• Set the unit
• Improve the visibility of the information on the bars

Create a chart

First create the structure of the data:

struct MoneyData: Identifiable {
    let id = UUID()
    let operation: Int
    let euro: Double
}

Then, add a chart to the View (note the import Charts):

import SwiftUI
import Charts

struct ContentView: View {
    @State var expences: [MoneyData] = [MoneyData]()
    var body: some View {
        VStack {
            Chart(expences, id: \.id) { ex in
                BarMark(
                    x: .value("Operation", ex.operation),
                    y: .value("Money", ex.euro)
                )
            }
            .frame(height: 300)
            .padding()
            .onAppear {
                self.expences = initMoney()
            }
        }
    }
    func initMoney() -> [MoneyData] {
        return [MoneyData(operation: 1, euro: 2.5),
                MoneyData(operation: 2, euro: 6.5), MoneyData(operation: 3, euro: 1.5)
        ]
    }
}

To have:

Next, the chart iterates over the expenses array, displaying the operation on the X-axis and the euros on the Y-axis.

To create a linear chart, use LineMark instead of BarMark:

LineMark(
         x: .value("Operation", ex.operation),
         y: .value("Money", ex.euro)
)

To have:

Note that the last operation has three values but is not displayed. To avoid this behavior, we need to add one value at the beginning and one at the end of the X-axis. Let’s see how to do this:

struct ContentView: View {
    @State var expences: [MoneyData] = [MoneyData]()
    @State var gridValue = [Int]()
    
    var body: some View {
        VStack {
            Chart(expences, id: \.id) { ex in
                LineMark(
                    x: .value("Operation", ex.operation),
                    y: .value("Money", ex.euro)
                )
            }.chartXAxis {
                AxisMarks(values: gridValue)  
            }
            .frame(height: 300)
            .padding()
            .onAppear {
                self.expences = initMoney()
                self.gridValue = Array((expences[0].operation - 1)...(expences[expences.count - 1].operation + 1))
            }
        }
    }
    func initMoney() -> [MoneyData] {
        return [MoneyData(operation: 1, euro: 2.5),
                MoneyData(operation: 2, euro: 6.5), MoneyData(operation: 3, euro: 1.5)
                
        ]
    }
}

First, we add a State variable gridValue, initialized in the onAppear method with an interval for the operation that is larger than the interval in the money data (e.g., [0,3] instead of [1,2]).

This interval is used by applying:

.chartXAxis {
                AxisMarks(values: gridValue)  
            }

Thus, we have:

Unit

Now, let’s see what happens if we use dates on the X-axis.

To use dates, first, adjust the data structure to include dates.

struct RunData: Identifiable {
    let id = UUID()
    let date: Date
    let km: Double
}

Then make some small changes in the code to use this type of data with the chart:

struct ContentView: View {
    @State var races: [RunData] = [RunData]()
    
    var body: some View {
        VStack {
            Chart(races, id: \.id) { run in
                BarMark(
                    x: .value("Date", run.date),
                    y: .value("Km", run.km)
                )
            }
            .frame(height: 300)
            .padding()
            .onAppear {
                self.races = initData()
            }
        }
    }
    func initData() -> [RunData] {
        let dateFormatter = ISO8601DateFormatter()
        dateFormatter.formatOptions = [.withFullDate]
        
        return [RunData(date: dateFormatter.date(from: "2024-05-03") ?? Date.now, km: 15),
                RunData(date: dateFormatter.date(from: "2024-05-05") ?? Date.now, km: 20),
                RunData(date: dateFormatter.date(from: "2024-05-07") ?? Date.now, km: 10)
        ]
    }
}

Simply, we replaced the moneyData with runData and used a different initialization function, just to have:

As you can see, we only have the label for “5 May.” Don’t worry, we have a simpler solution that I showed before. We can add the unit value for the X-axis:

BarMark(
         x: .value("Date", run.date, unit: .day),
         y: .value("Km", run.km)
)

Now we see:

Now you should have the knowledge base to implement charts in your app.

Note: English is not my native language, so I apologize for any errors. I use AI solely to generate the banner of the post; the content is human-generated.

In Xcode 15, we can display an alert using the .alert modifier.

Take a look at the code:

struct ContentView: View {
    @State var showAlert = false
    
    var body: some View {
        VStack {
            Button("Show Alert") {
                showAlert = true
            }
        }.alert("Important message", isPresented: $showAlert) {
            Button("OK", role: .cancel) {
                // Your action
            }
        }
        .padding()
    }
}

The role of the button can be:

• .cancel
• .destructive

struct ContentView: View {
    @State var showAlert = false
    
    var body: some View {
        VStack {
            Button("Show Alert") {
                showAlert = true
            }
        }.alert("Important message", isPresented: $showAlert) {
            Button("Delete", role: .destructive) {
                
            }
        }
        .padding()
    }
}

Note that using a button with .destructive is also added the default cancel button.

In this post, we’ll learn how to use LazyVGrid and LazyHGrid, two powerful and efficient grids to display multiple items.

The fundamental element for these types of grids is the GridItem, which can be of three types:

• .adaptive
• .fixed
• .flexible

GridItem Adaptive

GridItem Adaptive is essential for a responsive layout. By setting a minimum size for it, the grid will try to adapt to all the available space.

Take a look at using LazyHGrid:

struct ContentView: View {
    let rainbowColors = [Color.red, Color.orange, Color.yellow, Color.green, Color.mint, Color.teal, Color.cyan, Color.blue, Color.indigo, Color.purple, Color.brown]
    var body: some View {
        ScrollView(.horizontal) {
            LazyHGrid(rows: [GridItem(.adaptive(minimum:150))]) {
                        ForEach(rainbowColors, id:\.self) { color in
                            Circle()
                            .fill(color)
                        }
                    }
                    .padding()
                }
    }
}

We can also define different sizes for the rows:

ScrollView(.horizontal) {
            LazyHGrid(rows: [GridItem(.adaptive(minimum:150)),GridItem(.adaptive(minimum:100))]) {
                        ForEach(rainbowColors, id:\.self) { color in
                            Circle()
                                                    .fill(color)
                        }
                    }
                    .padding()
                }

So we have:

So, the two different dimensions are used to adapt to the screen.

This type is helpful when we have a dynamic number of elements, such as in a playlist.

Using the Vertical grid:

ScrollView() {
            LazyVGrid(columns: [GridItem(.adaptive(minimum:100)), GridItem(.adaptive(minimum:50)),GridItem(.adaptive(minimum:100))]) {
                        ForEach(rainbowColors, id:\.self) { color in
                            Circle()
                            .fill(color)
                        }
                    }
                    .padding()
                }
}

GridItem Fixed

In this case, the GridItem has a fixed size for the horizontal layout:

ScrollView(.horizontal) {
            LazyHGrid(rows: [GridItem(.fixed(100))]) {
                ForEach(rainbowColors, id:\.self) { color in
                    Circle()
                                            .fill(color)
                }
            }
            .padding()
        }

For vertical:

ScrollView() {
            LazyVGrid(columns: [GridItem(.fixed(100))]) {
                    ForEach(rainbowColors, id:\.self) { color in
                        Circle()
                        .fill(color)
                    }
                }
                .padding()
            }
}

This is helpful when you need a fixed number of columns or rows. In this case, by adding GridItem with a fixed size, we don’t have adaptability to the screen.

Take a look at this example:

ScrollView() {
            LazyVGrid(columns: [GridItem(.fixed(150)),GridItem(.fixed(150)),GridItem(.fixed(150))]) {
                    ForEach(rainbowColors, id:\.self) { color in
                        Circle()
                        .fill(color)
                    }
                }
                .padding()
            }

we have:

Three columns of circles with fixed size but truncated.

GridItem Flexible

With flexible, we define the size of GridItem within a range. For example:

ScrollView(.horizontal) {
            LazyHGrid(rows: [GridItem(.flexible(minimum: 10, maximum: 50)),GridItem(.flexible(minimum: 20, maximum: 100))]) {
                ForEach(rainbowColors, id:\.self) { color in
                    Circle()
                    .fill(color)
                }
            }
            .padding()
        }

To have:

It’s helpful when we need different sizes for different content, such as images and text.

Let’s try the vertical case for exercise.

Note: English is not my native language, so I apologize for any errors. I use AI solely to generate the banner of the post; the content is human-generated.